MediaWiki internal error.

Original exception: [47ba51b96d8a00ab269fc693] /s/de/index.php?title=:Datei_Diskussion:Bayrische_Abitur_2012_Analysis_I_1a.ggb/L%C3%B6schen&oldid=7585&diff=prev Wikimedia\Assert\PostconditionException from line 202 of /var/www/wiki/vendor/wikimedia/assert/src/Assert.php: Postcondition failed: makeTitleSafe() should always return a Title for the text returned by getRootText().
Backtrace:
#0 /var/www/wiki/includes/Title.php(1986): Wikimedia\Assert\Assert::postcondition()
#1 /var/www/wiki/includes/skins/Skin.php(480): Title->getRootTitle()
#2 /var/www/wiki/includes/OutputPage.php(3121): Skin->getPageClasses()
#3 /var/www/wiki/includes/skins/SkinTemplate.php(391): OutputPage->headElement()
#4 /var/www/wiki/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#5 /var/www/wiki/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#6 /var/www/wiki/includes/OutputPage.php(2615): SkinTemplate->outputPage()
#7 /var/www/wiki/includes/MediaWiki.php(947): OutputPage->output()
#8 /var/www/wiki/includes/MediaWiki.php(960): MediaWiki->{closure}()
#9 /var/www/wiki/includes/MediaWiki.php(543): MediaWiki->main()
#10 /var/www/wiki/index.php(51): MediaWiki->run()
#11 /var/www/wiki/index.php(44): wfIndexMain()
#12 {main}

Exception caught inside exception handler: [47ba51b96d8a00ab269fc693] /s/de/index.php?title=:Datei_Diskussion:Bayrische_Abitur_2012_Analysis_I_1a.ggb/L%C3%B6schen&oldid=7585&diff=prev Wikimedia\Assert\PostconditionException from line 202 of /var/www/wiki/vendor/wikimedia/assert/src/Assert.php: Postcondition failed: makeTitleSafe() should always return a Title for the text returned by getRootText().
Backtrace:
#0 /var/www/wiki/includes/Title.php(1986): Wikimedia\Assert\Assert::postcondition()
#1 /var/www/wiki/includes/skins/Skin.php(480): Title->getRootTitle()
#2 /var/www/wiki/includes/OutputPage.php(3121): Skin->getPageClasses()
#3 /var/www/wiki/includes/skins/SkinTemplate.php(391): OutputPage->headElement()
#4 /var/www/wiki/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#5 /var/www/wiki/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#6 /var/www/wiki/includes/OutputPage.php(2615): SkinTemplate->outputPage()
#7 /var/www/wiki/includes/exception/MWExceptionRenderer.php(153): OutputPage->output()
#8 /var/www/wiki/includes/exception/MWExceptionRenderer.php(65): MWExceptionRenderer::reportHTML()
#9 /var/www/wiki/includes/exception/MWExceptionHandler.php(106): MWExceptionRenderer::output()
#10 /var/www/wiki/includes/exception/MWExceptionHandler.php(185): MWExceptionHandler::report()
#11 /var/www/wiki/includes/MediaWiki.php(576): MWExceptionHandler::handleException()
#12 /var/www/wiki/index.php(51): MediaWiki->run()
#13 /var/www/wiki/index.php(44): wfIndexMain()
#14 {main}