Fix Nu Html Checker issues

Fix various Nu Html Checker issues in dropzone (print_api.php):

• Error: Element img is missing required attribute src.
• Error: An img element must have an alt attribute, except under certain
  conditions.

In bug_view_inc.php:

• Error: Element tbody not allowed as child of element table in this
  context.
• Error: Duplicate ID history.

In bug_update_page.php and bugnote_view_inc.php:

• Error: The width attribute on the td element is obsolete.
• Warning: A table row was 0 columns wide, which is less than the column
  count established by the first row (6).
• Error: Element option without attribute label must not be empty.
• Error: Duplicate ID bugnotes.

In print_all_bug_page.php:

• Error: Stray end tag td.
• Error: Row 2 of a row group established by a tbody element has no
  cells beginning on it.
• Warning: A table row was 10 columns wide and exceeded the column count
  established by the first row (5).

In print_all_bug_page_word.php:

• Error: The width attribute on the td element is obsolete.
• Error: Row 2 of a row group established by a tbody element has no
  cells beginning on it.