bug_actiongroup.php: Clean up error handling.

- Always check the requester's access first.

- Associate each check directly with an error message, instead of
  performing all checks and going back to see which one failed.

- New error messages distinct from the general "permission denied"
  message when assigning an issue to a disallowed handler or setting a
  version that does not exist in the project.

Includes string changes for English only.

diff --git a/bug_actiongroup.php b/bug_actiongroup.php
index 4e70bb1..a378242 100644
--- a/bug_actiongroup.php
+++ b/bug_actiongroup.php
@@ -107,19 +107,17 @@ foreach( $f_bug_arr as $t_bug_id ) {
 
 	case 'CLOSE':
 		$t_closed = config_get( 'bug_closed_status_threshold' );
-		if ( access_can_close_bug( $t_bug_id ) &&
-				( $t_status < $t_closed ) &&
+		if ( access_can_close_bug( $t_bug_id ) ) {
+			if ( ( $t_status < $t_closed ) &&
 				bug_check_workflow( $t_status, $t_closed ) ) {
-
-			/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $f_bug_id, $t_bug_data, $f_bugnote_text ) ); */
-			bug_close( $t_bug_id, $f_bug_notetext, $f_bug_noteprivate );
-			helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
-		} else {
-			if ( !access_can_close_bug( $t_bug_id ) ) {
-				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
+				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $f_bug_id, $t_bug_data, $f_bugnote_text ) ); */
+				bug_close( $t_bug_id, $f_bug_notetext, $f_bug_noteprivate );
+				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
 			} else {
 				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_status' );
 			}
+		} else {
+			$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
 		}
 		break;
 
@@ -163,38 +161,38 @@ foreach( $f_bug_arr as $t_bug_id ) {
 		# check that new handler has rights to handle the issue, and
 		#  that current user has rights to assign the issue
 		$t_threshold = access_get_status_threshold( $t_assign_status, bug_get_field( $t_bug_id, 'project_id' ) );
-		if ( access_has_bug_level( $t_threshold , $t_bug_id, $f_assign ) &&
-			 access_has_bug_level( config_get( 'update_bug_assign_threshold', config_get( 'update_bug_threshold' ) ), $t_bug_id ) &&
-				bug_check_workflow($t_status, $t_assign_status )	) {
-			/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
-			bug_assign( $t_bug_id, $f_assign, $f_bug_notetext, $f_bug_noteprivate );
-			helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
-		} else {
-			if ( bug_check_workflow($t_status, $t_assign_status ) ) {
-				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
+		if ( access_has_bug_level( config_get( 'update_bug_assign_threshold', config_get( 'update_bug_threshold' ) ), $t_bug_id ) ) {
+			if ( access_has_bug_level( $t_threshold , $t_bug_id, $f_assign ) ) {
+				if ( bug_check_workflow($t_status, $t_assign_status ) ) {
+					/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
+					bug_assign( $t_bug_id, $f_assign, $f_bug_notetext, $f_bug_noteprivate );
+					helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
+				} else {
+					$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_status' );
+				}
 			} else {
-				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_status' );
+				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_handler' );
 			}
+		} else {
+			$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
 		}
 		break;
 
 	case 'RESOLVE':
 		$t_resolved_status = config_get( 'bug_resolved_status_threshold' );
-		if ( access_has_bug_level( access_get_status_threshold( $t_resolved_status, bug_get_field( $t_bug_id, 'project_id' ) ), $t_bug_id ) &&
-					( $t_status < $t_resolved_status ) &&
-					bug_check_workflow($t_status, $t_resolved_status ) ) {
-			$f_resolution = gpc_get_int( 'resolution' );
-			$f_fixed_in_version = gpc_get_string( 'fixed_in_version', '' );
-			/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
-			bug_resolve( $t_bug_id, $f_resolution, $f_fixed_in_version, $f_bug_notetext, null, null, $f_bug_noteprivate );
-			helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
-		} else {
+		if ( access_has_bug_level( access_get_status_threshold( $t_resolved_status, bug_get_field( $t_bug_id, 'project_id' ) ), $t_bug_id ) ) {
 			if ( ( $t_status < $t_resolved_status ) &&
 					bug_check_workflow($t_status, $t_resolved_status ) ) {
-				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
+				$f_resolution = gpc_get_int( 'resolution' );
+				$f_fixed_in_version = gpc_get_string( 'fixed_in_version', '' );
+				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
+				bug_resolve( $t_bug_id, $f_resolution, $f_fixed_in_version, $f_bug_notetext, null, null, $f_bug_noteprivate );
+				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
 			} else {
 				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_status' );
 			}
+		} else {
+			$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
 		}
 		break;
 
@@ -249,18 +247,16 @@ foreach( $f_bug_arr as $t_bug_id ) {
 	case 'UP_FIXED_IN_VERSION':
 		$f_fixed_in_version = gpc_get_string( 'fixed_in_version' );
 		$t_project_id = bug_get_field( $t_bug_id, 'project_id' );
-		$t_success = false;
 
 		if ( access_has_bug_level( config_get( 'update_bug_threshold' ), $t_bug_id ) ) {
 			if ( version_get_id( $f_fixed_in_version, $t_project_id ) !== false ) {
 				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
 				bug_set_field( $t_bug_id, 'fixed_in_version', $f_fixed_in_version );
 				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
-				$t_success = true;
+			} else {
+				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_version' );
 			}
-		}
-
-		if ( !$t_success ) {
+		} else {
 			$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
 		}
 		break;
@@ -268,18 +264,16 @@ foreach( $f_bug_arr as $t_bug_id ) {
 	case 'UP_TARGET_VERSION':
 		$f_target_version = gpc_get_string( 'target_version' );
 		$t_project_id = bug_get_field( $t_bug_id, 'project_id' );
-		$t_success = false;
 
 		if ( access_has_bug_level( config_get( 'roadmap_update_threshold' ), $t_bug_id ) ) {
 			if ( version_get_id( $f_target_version, $t_project_id ) !== false ) {
 				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
 				bug_set_field( $t_bug_id, 'target_version', $f_target_version );
 				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
-				$t_success = true;
+			} else {
+				$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_version' );
 			}
-		}
-
-		if ( !$t_success ) {
+		} else {
 			$t_failed_ids[$t_bug_id] = lang_get( 'bug_actiongroup_access' );
 		}
 		break;
diff --git a/lang/strings_english.txt b/lang/strings_english.txt
index cced653..60e5055 100644
--- a/lang/strings_english.txt
+++ b/lang/strings_english.txt
@@ -139,8 +139,10 @@ $s_select_option = '(select)'; # comboboxes default to this to instruct user to
 
 # bug_actiongroup_page.php : mass treatment
 $s_bug_actiongroup_access = 'You did not have appropriate permissions to perform that action.';
-$s_bug_actiongroup_status = 'This issue cannot be changed to the requested status';
-$s_bug_actiongroup_category = 'This issue cannot be changed to the requested category';
+$s_bug_actiongroup_status = 'The requested status change is not allowed by the workflow.';
+$s_bug_actiongroup_handler = 'The requested handler is not allowed to handle this issue.';
+$s_bug_actiongroup_category = 'The requested category does not exist.';
+$s_bug_actiongroup_version = 'The requested version does not exist in this issue\'s project.';
 $s_close_bugs_conf_msg = 'Are you sure you wish to close these issues?';
 $s_delete_bugs_conf_msg = 'Are you sure you wish to delete these issues?';
 $s_move_bugs_conf_msg = 'Move issues to';

bug_actiongroup.php: Allow setting an empty version.

diff --git a/bug_actiongroup.php b/bug_actiongroup.php
index a378242..7c0ab32 100644
--- a/bug_actiongroup.php
+++ b/bug_actiongroup.php
@@ -249,7 +249,7 @@ foreach( $f_bug_arr as $t_bug_id ) {
 		$t_project_id = bug_get_field( $t_bug_id, 'project_id' );
 
 		if ( access_has_bug_level( config_get( 'update_bug_threshold' ), $t_bug_id ) ) {
-			if ( version_get_id( $f_fixed_in_version, $t_project_id ) !== false ) {
+			if ( $f_fixed_in_version === '' || version_get_id( $f_fixed_in_version, $t_project_id ) !== false ) {
 				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
 				bug_set_field( $t_bug_id, 'fixed_in_version', $f_fixed_in_version );
 				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );
@@ -266,7 +266,7 @@ foreach( $f_bug_arr as $t_bug_id ) {
 		$t_project_id = bug_get_field( $t_bug_id, 'project_id' );
 
 		if ( access_has_bug_level( config_get( 'roadmap_update_threshold' ), $t_bug_id ) ) {
-			if ( version_get_id( $f_target_version, $t_project_id ) !== false ) {
+			if ( $f_target_version === '' || version_get_id( $f_target_version, $t_project_id ) !== false ) {
 				/** @todo we need to issue a helper_call_custom_function( 'issue_update_validate', array( $t_bug_id, $t_bug_data, $f_bugnote_text ) ); */
 				bug_set_field( $t_bug_id, 'target_version', $f_target_version );
 				helper_call_custom_function( 'issue_update_notify', array( $t_bug_id ) );