Problem description: in IE11 and Edge browsers at certain zoom values scrollbars are visible in overlay dialogues the content of which isn't even loaded yet.

Steps to reproduce:

1. Open zabbix frontend using Edge or IE11 browser
2. Navigate to any view where an overlay dialogue can be opened (like dashboard in edit mode)
3. Disconnect your internet connection or simulate slow network in any other way
4. Launch the overlay dialogue (edit a widget)

Result: a scrollbar is visible in the opened overlay dialogue even though the content of the overlay isn't even loaded at all. If there is no scrollbar try zooming in and out.
Expected: there should be no scrollbar in such cases.

Example: