…/showthread.php(1617).

…hread.php` and `forumdisplay.php`, reported in mybb#4530 (comment) .

…ivate.php`(1812).

…ewthread.php` (1093).

…ull in `usercp.php` (L3643).

…ray key 0 in `inc/class_parser.php` (L1494, L1587).

 - Delayed moderation:
    - Undefined variable `$thread` in `moderation.php` (L423).
    - Trying to access array offset on value of type null in `moderation.php` (L423).

 - Soft delete thread(s):
    - Undefined array key "num_threads" in `inc/class_moderation.php` (L3798).
    - Undefined array key "num_threads" in `inc/class_moderation.php` (L3798).

 - Restore (soft-deleted) thread(s):
    - Undefined array key "num_threads" in `inc/class_moderation.php` (L3639).
    - Undefined array key "num_threads" in `inc/class_moderation.php` (L3639).

 - Move post(s):
    - Undefined variable `$return_url` in eval()'d code (L27) in `moderation.php` (L2669).

 - Moving post(s):
    - Undefined array key 1 in `moderation.php` (L2697).

 - Approve thread(s):
    - Undefined array key XXX in `inc/class_moderation.php` (L437).
    - Undefined array key "num_posts" in `inc/class_moderation.php` (L437).
    - Undefined array key "num_threads" in `inc/class_moderation.php` (L504).

 - Similarly, unapprove thread(s).

…ull `polls.php` (L983).

… UTF-8 Conversion:

 - Undefined array key "table" in `admin/modules/tools/system_health.php` (L441).
 - Undefined variable `$converting_table` in `admin/modules/tools/system_health.php` (L241).
 - Undefined variable `$fulltext_to_create` in `admin/modules/tools/system_health.php` (L360).

…n `/admin/modules/tools/modlog.php` (L313).

…, which results in PHP fatal error of uncaught TypeError: Argument #2 ($array) must be of type array, null given in `array_key_exists()` in `/inc/datahandler.php` (L207).

…efinements in `send_pm()` in `inc/functions.php` (L9027).

…rify_sender()` in `inc/datahandlers/pm.php` (L149-L150), a workaround for mybb#4630 (comment) .

…orumlist.php` (L490).

 - Undefined array key "pid" in `inc/datahandlers/warnings.php` (L687) when issuing a warning from user profile page, etc.
 - Undefined variable `$last_expired` in `warnings.php` (L238) when viewing a user's warnings for their specific post.

…php` (L1213) and a typo in `inc/datahandlers/post.php` (L1228).

…t.php` (L106).

…ibility issues.