The navbar "more" menu sometimes hidden behind toolbar

How to reproduce

• Login as administrator that has many sites and a "more"
• Open a course
• Click the "more" menu in the sites top nav
• => OK: more menu visible
• Open a survey learning resource
• Open the content editor
• Click the "more" menu in the sites top nav
• => NOK: more menu hidden behind toolbar
• Go to a course
• Click the "more" menu in the sites top nav
• => NOK: more menu also hidden where it worked before

In the DOM a z-index of 5 is applied to the #o_main_wrapper. This is cause by jquery.contenteditor.v2.js in line 31 whenever the content editor is loaded. 

The z-index hierarchy must be revised in a way that the "more"-menu is always above the toolbar.