VirtualBox on Ubuntu 19.10 shows no VM-icon in dock

Recently i've upgraded ubuntu from 18.04 to 19.10. Everything is working fine as im used from ubuntu. Exept that VirtualBox dont show the Icon the the VM which is currently running. The Icon of the VM Manager appears normal but the icon of the current running VM is just a blank space

I've also upgraded VirtualBox to the latest Version 6.1 but it didn't fix the problem. I guess its a gnome issue beacuse ive never faced this kind of issue with a diffrent distro or DE like MX 19 or Kubuntu 19.10.

Any suggestion is much appreciated.

The workaround is to move window to another workspace.

This bug and the workaround is posted here: https://www.virtualbox.org/ticket/18705

In my case (Ubuntu 20.04 host, W7 guest) icon appears again after switching "Ctrl+L" to normal mode and "Ctrl+L" back to seamless mode.