MediaWiki internal error.

Original exception: [6df0f90fdf2e805468c9c8de] /wiki/Vorlage:/ InvalidArgumentException from line 276 of /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Title.php: $text must be a string.
Backtrace:
#0 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/user/User.php(1225): Title::newFromText(boolean, integer)
#1 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/user/User.php(595): User::getCanonicalName(boolean, string)
#2 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/extensions/MenuSidebar/MenuSidebar.php(70): User::newFromName(boolean)
#3 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Hooks.php(177): fnMenuSidebar(SkinVector, array)
#4 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Hooks.php(205): Hooks::callHook(string, array, array, NULL)
#5 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/Skin.php(1262): Hooks::run(string, array)
#6 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/Skin.php(1287): Skin->{closure}()
#7 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/SkinTemplate.php(481): Skin->buildSidebar()
#8 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/SkinTemplate.php(249): SkinTemplate->prepareQuickTemplate()
#9 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/OutputPage.php(2388): SkinTemplate->outputPage()
#10 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/MediaWiki.php(825): OutputPage->output(boolean)
#11 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/MediaWiki.php(837): MediaWiki->{closure}()
#12 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/MediaWiki.php(524): MediaWiki->main()
#13 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/index.php(42): MediaWiki->run()
#14 {main}

Exception caught inside exception handler: [6df0f90fdf2e805468c9c8de] /wiki/Vorlage:/ InvalidArgumentException from line 276 of /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Title.php: $text must be a string.
Backtrace:
#0 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/user/User.php(1225): Title::newFromText(boolean, integer)
#1 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/user/User.php(595): User::getCanonicalName(boolean, string)
#2 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/extensions/MenuSidebar/MenuSidebar.php(70): User::newFromName(boolean)
#3 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Hooks.php(177): fnMenuSidebar(SkinVector, array)
#4 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/Hooks.php(205): Hooks::callHook(string, array, array, NULL)
#5 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/Skin.php(1262): Hooks::run(string, array)
#6 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/Skin.php(1287): Skin->{closure}()
#7 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/SkinTemplate.php(481): Skin->buildSidebar()
#8 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/skins/SkinTemplate.php(249): SkinTemplate->prepareQuickTemplate()
#9 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/OutputPage.php(2388): SkinTemplate->outputPage()
#10 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/exception/MWExceptionRenderer.php(137): OutputPage->output()
#11 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/exception/MWExceptionRenderer.php(54): MWExceptionRenderer::reportHTML(InvalidArgumentException)
#12 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/exception/MWExceptionHandler.php(75): MWExceptionRenderer::output(InvalidArgumentException, integer)
#13 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/exception/MWExceptionHandler.php(149): MWExceptionHandler::report(InvalidArgumentException)
#14 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/includes/MediaWiki.php(551): MWExceptionHandler::handleException(InvalidArgumentException)
#15 /var/www/info/mobadaten/htdocs/MoBaDatenInfo/index.php(42): MediaWiki->run()
#16 {main}