Fix more issues detected by Nu Html Checker

In bug_update_page.php:

• Error: The first child option element of a select element with a
  required attribute, and without a multiple attribute, and without
  a size attribute whose value is greater than 1, must have either an
  empty value attribute, or must have no text content.
• Error: Element option without attribute label must not be empty.

In bug_change_status_page.php:

• Error: Start tag input seen in table.
• Error: Element option without attribute label must not be empty.
• Error: End tag div seen, but there were open elements.
• Error: Unclosed element fieldset.

In bug_report_page.php:

• Error: Element option without attribute label must not be empty.
• Error: The value of the for attribute of the label element must be
  the ID of a non-hidden form control.

In manage_user_create_page.php:

• Error: Start tag fieldset seen in table.
• Error: Unclosed element div.

In bug_view_inc.php (called via view.php):

• Error: Row 1 of a row group established by a thead element has no
  cells beginning on it.
• Error: Element option without attribute label must not be empty.