Issue Summary

Adding <aui-dropdown-menu> dropdown menu causes the editor to stop working.

Steps to Reproduce

1. Install an app that adds an <aui-dropdown-menu> element to the #main-content section of a page in view mode.
2. Visit any page.
3. Click the `Edit` button so that the page goes in to quick edit mode.

Expected Results

The editor can be used.

Actual Results

The editor becomes unusable:

• Cannot scroll to the bottom of the editor content
• Some toolbar buttons are duplicated
• Several editor behaviours don't work as expected

Workaround

There are a few options here:

• Recommended: Before disabling any apps, please try to upgrade them since there might be a new version which contains a workaround to prevent the issue in the first place.
• Problematic apps can be disabled.