Overlay dialogue behaviour when open debug mode

There are several strange behaviours when overlay dialogue is open (e.g. widget edit form) and debug mode is on/off .

Steps to reproduce:

1. Edit problems widget
2. Turn on debug mode
   Result: widget on the right; apply/cancel widget buttons not available and isn't visible all debug info (except Firefox)
3. Add tag line in widget
   Result: widget window on whole screen now (except Firefox). In Firefox every time when add tag - window size increases.
4. Hide debug
   Result: widget window on the left