Prototype is broken in inline mode when having extra form element in contentmenu

Adding extra form element into #contentmenu breaks functionality of prototype.js in inline mode.

Steps to reproduce:
1) open xwiki/skins/flamingo/menus_content.vm
2) add <form></form> (or any other form element) after second line (into #contentmenu)
3) access xwiki -> buttons when editing user profile don't work, AWM step 2 is not working, etc.