"User Profil" - Error in existing project

Hello,
I have transferred a project from 10.4 (V.36153) to 10.5 (V.36478).
In the new application (from 10.5) there is now without any action in a small menu (right above, at the LogOut) the selection "User Profile".
After pressing the same I get the following error message:

===
Fatal error: Call to a member function exists() on a non-object in C:\xampp\htdocs\Alaska_105\classes\editpage.php on line 281
===
Line 279-285 in editpage.php:

	public function init()
	{
		if( $this->eventsObject->exists("BeforeProcessEdit") )
			$this->eventsObject->BeforeProcessEdit( $this );

		parent::init();
	}

I have already rebuilt all pages (using the "Reset all Pages" button) in the editor area, but unfortunately it didn't help.
Is this a general understandable error/compatibility problem, or did I not consider something?

If I create a new project under V.10.5 the menu item "User-Profile" works !

Does anyone have an idea where it crunches?

Thanks in advance and best regards

Michael