Internal error

[ZiFDZG7FzIxFykkQ8QWSagAAVyI] /index.php?title=Bleakworld&oldid=21786 Error from line 1573 of /home/msh7m8p36sck/public_html/includes/page/Article.php: Call to a member function getTimestamp() on null

Backtrace:

#0 /home/msh7m8p36sck/public_html/includes/page/Article.php(711): Article->setOldSubtitle(integer)
#1 /home/msh7m8p36sck/public_html/includes/actions/ViewAction.php(63): Article->view()
#2 /home/msh7m8p36sck/public_html/includes/MediaWiki.php(511): ViewAction->show()
#3 /home/msh7m8p36sck/public_html/includes/MediaWiki.php(302): MediaWiki->performAction(Article, Title)
#4 /home/msh7m8p36sck/public_html/includes/MediaWiki.php(900): MediaWiki->performRequest()
#5 /home/msh7m8p36sck/public_html/includes/MediaWiki.php(527): MediaWiki->main()
#6 /home/msh7m8p36sck/public_html/index.php(44): MediaWiki->run()
#7 {main}