This problem usually we face in 3 scenarios for drupal
1. when we update Jquery Update to new version. This scenario we can easily solve it by reverting back to old version.And be cautious, while doing any updates in drupal, try to do it in test environment later try in rela time.
2. When we try to fulfill our requirement by hard coding like adding .js files manually instead of using modules. To solve this, our first step is we need to find by which file adding we are getting this error.So try to remove each js file which you added manually and test at admin side still problem persists or not?(Don't forget to remove cache for each trial). Continue this until problem solved.
3. Sometimes when we install some new modules also we face this problem, because sometimes the js files which are used in new module may be not adjusted to old module js files. So uninstall newly added module and check again.
