MediaWiki internal error.

Original exception: [8a1cb8cef1692abfb6908894] /index.php?direction=prev&oldid=20538&title=Samuel-034 Error: Using $this when not in object context
Backtrace:
from /home/common/header.php(235)
#0 /home/wikihalo/www/LocalSettings.php(373): include()
#1 /home/wikihalo/www/includes/HookContainer/HookContainer.php(159): fnAfterAll()
#2 /home/wikihalo/www/includes/HookContainer/HookRunner.php(650): MediaWiki\HookContainer\HookContainer->run()
#3 /home/wikihalo/www/includes/Output/OutputPage.php(3202): MediaWiki\HookContainer\HookRunner->onAfterFinalPageOutput()
#4 /home/wikihalo/www/includes/actions/ActionEntryPoint.php(163): MediaWiki\Output\OutputPage->output()
#5 /home/wikihalo/www/includes/MediaWikiEntryPoint.php(200): MediaWiki\Actions\ActionEntryPoint->execute()
#6 /home/wikihalo/www/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#7 {main}

Exception caught inside exception handler: [8a1cb8cef1692abfb6908894] /index.php?direction=prev&oldid=20538&title=Samuel-034 Error: Using $this when not in object context
Backtrace:
from /home/common/header.php(235)
#0 /home/wikihalo/www/LocalSettings.php(373): include()
#1 /home/wikihalo/www/includes/HookContainer/HookContainer.php(159): fnAfterAll()
#2 /home/wikihalo/www/includes/HookContainer/HookRunner.php(650): MediaWiki\HookContainer\HookContainer->run()
#3 /home/wikihalo/www/includes/Output/OutputPage.php(3202): MediaWiki\HookContainer\HookRunner->onAfterFinalPageOutput()
#4 /home/wikihalo/www/includes/exception/MWExceptionRenderer.php(190): MediaWiki\Output\OutputPage->output()
#5 /home/wikihalo/www/includes/exception/MWExceptionRenderer.php(109): MWExceptionRenderer::reportHTML()
#6 /home/wikihalo/www/includes/exception/MWExceptionHandler.php(135): MWExceptionRenderer::output()
#7 /home/wikihalo/www/includes/exception/MWExceptionHandler.php(239): MWExceptionHandler::report()
#8 /home/wikihalo/www/includes/MediaWikiEntryPoint.php(222): MWExceptionHandler::handleException()
#9 /home/wikihalo/www/includes/actions/ActionEntryPoint.php(82): MediaWiki\MediaWikiEntryPoint->handleTopLevelError()
#10 /home/wikihalo/www/includes/MediaWikiEntryPoint.php(206): MediaWiki\Actions\ActionEntryPoint->handleTopLevelError()
#11 /home/wikihalo/www/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#12 {main}