Not a (direct) showstopper as such.
When a page-title change would result in an empty page-title it triggered the following error. (Replace_text form interface)
[ZLjjNw_BJjdvj9s8jky3lgAAAAQ] /wiki/Special:ReplaceText TypeError: Argument 2 passed to MediaWiki\Page\PageCommandFactory::newMovePage() must be an instance of Title, null given, called in /var/www/mediawiki-1.39.0/extensions/ReplaceText/src/SpecialReplaceText.php on line 386
Backtrace:
from /var/www/mediawiki-1.39.0/includes/page/PageCommandFactory.php(300)
#0 /var/www/mediawiki-1.39.0/extensions/ReplaceText/src/SpecialReplaceText.php(386): MediaWiki\Page\PageCommandFactory->newMovePage(Title, NULL)
#1 /var/www/mediawiki-1.39.0/extensions/ReplaceText/src/SpecialReplaceText.php(186): MediaWiki\Extension\ReplaceText\SpecialReplaceText->getTitlesForMoveAndUnmoveableTitles()
#2 /var/www/mediawiki-1.39.0/extensions/ReplaceText/src/SpecialReplaceText.php(82): MediaWiki\Extension\ReplaceText\SpecialReplaceText->doSpecialReplaceText()
#3 /var/www/mediawiki-1.39.0/includes/specialpage/SpecialPage.php(701): MediaWiki\Extension\ReplaceText\SpecialReplaceText->execute(NULL)
#4 /var/www/mediawiki-1.39.0/includes/specialpage/SpecialPageFactory.php(1428): SpecialPage->run(NULL)
#5 /var/www/mediawiki-1.39.0/includes/MediaWiki.php(316): MediaWiki\SpecialPage\SpecialPageFactory->executePath(string, RequestContext)
#6 /var/www/mediawiki-1.39.0/includes/MediaWiki.php(904): MediaWiki->performRequest()
#7 /var/www/mediawiki-1.39.0/includes/MediaWiki.php(562): MediaWiki->main()
#8 /var/www/mediawiki-1.39.0/index.php(50): MediaWiki->run()
#9 /var/www/mediawiki-1.39.0/index.php(46): wfIndexMain()
#10 {main}
MediaWiki: 1.39.0 PHP: 7.4.33 (fpm-fcgi) MariaDB: 10.5.19-MariaDB ICU: 50.2
Replace Text 1.7 (cba3752) 18:03, 14 March 2023
Related page could potentially be flagged as invalid case, and skipped as such.
Potentially printing that there where cases skipped because of the empty page-title replacement result.