Zoom looses focus in advanced mode while crossing chart border

[TheWitness]

Describe the bug
Due to some issues in CSS, in some browsers, the advanced mode in Zoom does not function well.

To Reproduce
Steps to reproduce the behavior:

1. Setup Advanced mode in zoom
2. Set the two boundaries
3. Attempt to click on anchors and resize the zoom menu before triggering
4. Note that you can not resize the window once established.

Expected behavior
Cacti should allow you to resize the window before activating it.

[TheWitness]

Closed by 209d1ab