MediaWiki internal error.

Original exception: exception 'MWException' with message 'Detected bug in an extension! Hook efGoogleAnalyticsHookText failed to return a value; should return true to continue hook processing or false to abort.' in C:\wwwroot\www\wikibond.nl\includes\Hooks.php:137
Stack trace:
#0 C:\wwwroot\www\wikibond.nl\includes\Skin.php(754): wfRunHooks('SkinAfterBottom...', Array)
#1 C:\wwwroot\www\wikibond.nl\includes\SkinTemplate.php(404): Skin->bottomScripts()
#2 C:\wwwroot\www\wikibond.nl\includes\OutputPage.php(821): SkinTemplate->outputPage(Object(OutputPage))
#3 C:\wwwroot\www\wikibond.nl\includes\Wiki.php(337): OutputPage->output()
#4 C:\wwwroot\www\wikibond.nl\index.php(94): MediaWiki->finalCleanup(Array, Object(OutputPage))
#5 {main}

Exception caught inside exception handler: exception 'MWException' with message 'Detected bug in an extension! Hook efGoogleAnalyticsHookText failed to return a value; should return true to continue hook processing or false to abort.' in C:\wwwroot\www\wikibond.nl\includes\Hooks.php:137
Stack trace:
#0 C:\wwwroot\www\wikibond.nl\includes\Skin.php(754): wfRunHooks('SkinAfterBottom...', Array)
#1 C:\wwwroot\www\wikibond.nl\includes\SkinTemplate.php(404): Skin->bottomScripts()
#2 C:\wwwroot\www\wikibond.nl\includes\OutputPage.php(821): SkinTemplate->outputPage(Object(OutputPage))
#3 C:\wwwroot\www\wikibond.nl\includes\Exception.php(150): OutputPage->output()
#4 C:\wwwroot\www\wikibond.nl\includes\Exception.php(174): MWException->reportHTML()
#5 C:\wwwroot\www\wikibond.nl\includes\Exception.php(260): MWException->report()
#6 C:\wwwroot\www\wikibond.nl\includes\Exception.php(303): wfReportException(Object(MWException))
#7 [internal function]: wfExceptionHandler(Object(MWException))
#8 {main}