Panel in hiding mode flickers when opening application menu
## Submitted by Yousuf Philips `@philipzae`
Assigned to **Xfce Bug Triage**
**[Link to original bug (#16765)](https://bugzilla.xfce.org/show_bug.cgi?id=16765)**
## Description
Steps:
1. add classic application menu to panel
2. set panel to always hide
3. click to open application menu
4. notice flicker in the menu
https://youtu.be/wVJVixbF5hQ (flicker appears at 00:29)
Version: Unspecified
issue