I can confirm I have display errors turned on in php.ini, however an error still occurs when submitting the edited template... as others have said the fix isn't working, though with s810car's modified conditional
PHP Code:
<if condition="(THIS_SCRIPT == 'indexTAB' AND (in_array($forum['forumid'], $GLOBALS[tabcats]) OR in_array('all', $GLOBALS[tabcats]))) OR (THIS_SCRIPT == 'forumdisplay')">
no errors. The parenthesis are what made it work, the quotes around forumid didn't make a difference. The All Forums module still won't display, though that may just be an error on my end since I haven't heard anyone else mention that.