There is a problem with your MediaWiki codebase. For us to understand what you are going through please could you provide more information about what happened? The current state of your mediawiki and database? Also, could you make sure that you have updated your DB running the "php maintenance/update.php" script?

One more thing you need to know is that if you are using an extension, make sure to put in in the LocalSettings.php file and make sure your local repo is up to date by typing the command "git pull origin master" before making a PR. Check to make sure all these has been done before trying to make the PR again or seeing if you will get the error.