MediaWiki internal error.

Original exception: [dff49588c6301531c8d85619] /w/index.php?title=Property:Mouse_sensitivity&oldid=189639 Wikimedia\Assert\PostconditionException from line 202 of /opt/mediawiki/w/vendor/wikimedia/assert/src/Assert.php: Postcondition failed: makeTitleSafe() should always return a Title for the text returned by getRootText().
Backtrace:
#0 /opt/mediawiki/w/includes/Title.php(1995): Wikimedia\Assert\Assert::postcondition()
#1 /opt/mediawiki/w/includes/skins/Skin.php(480): Title->getRootTitle()
#2 /opt/mediawiki/w/includes/OutputPage.php(3128): Skin->getPageClasses()
#3 /opt/mediawiki/w/includes/skins/SkinTemplate.php(405): OutputPage->headElement()
#4 /opt/mediawiki/w/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#5 /opt/mediawiki/w/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#6 /opt/mediawiki/w/includes/OutputPage.php(2622): SkinTemplate->outputPage()
#7 /opt/mediawiki/w/includes/MediaWiki.php(954): OutputPage->output()
#8 /opt/mediawiki/w/includes/MediaWiki.php(967): MediaWiki->{closure}()
#9 /opt/mediawiki/w/includes/MediaWiki.php(547): MediaWiki->main()
#10 /opt/mediawiki/w/index.php(53): MediaWiki->run()
#11 /opt/mediawiki/w/index.php(46): wfIndexMain()
#12 {main}

Exception caught inside exception handler: [dff49588c6301531c8d85619] /w/index.php?title=Property:Mouse_sensitivity&oldid=189639 Wikimedia\Assert\PostconditionException from line 202 of /opt/mediawiki/w/vendor/wikimedia/assert/src/Assert.php: Postcondition failed: makeTitleSafe() should always return a Title for the text returned by getRootText().
Backtrace:
#0 /opt/mediawiki/w/includes/Title.php(1995): Wikimedia\Assert\Assert::postcondition()
#1 /opt/mediawiki/w/includes/skins/Skin.php(480): Title->getRootTitle()
#2 /opt/mediawiki/w/includes/OutputPage.php(3128): Skin->getPageClasses()
#3 /opt/mediawiki/w/includes/skins/SkinTemplate.php(405): OutputPage->headElement()
#4 /opt/mediawiki/w/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#5 /opt/mediawiki/w/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#6 /opt/mediawiki/w/includes/OutputPage.php(2622): SkinTemplate->outputPage()
#7 /opt/mediawiki/w/includes/exception/MWExceptionRenderer.php(153): OutputPage->output()
#8 /opt/mediawiki/w/includes/exception/MWExceptionRenderer.php(65): MWExceptionRenderer::reportHTML()
#9 /opt/mediawiki/w/includes/exception/MWExceptionHandler.php(106): MWExceptionRenderer::output()
#10 /opt/mediawiki/w/includes/exception/MWExceptionHandler.php(185): MWExceptionHandler::report()
#11 /opt/mediawiki/w/includes/MediaWiki.php(580): MWExceptionHandler::handleException()
#12 /opt/mediawiki/w/index.php(53): MediaWiki->run()
#13 /opt/mediawiki/w/index.php(46): wfIndexMain()
#14 {main}