Notification dot suddenly envelop symbol
After switching to KDE and back to Gnome on Ubuntu 18.04 LTS the notification dot suddenly turned into an envelop symbol:
GNOME Shell 3.28.3
Linux XXXXXXXXX 4.19.0-041900-generic #201810221809 SMP Mon Oct 22 22:11:45 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic
What is the reason for this / how can this be fixed (I want the old notification dot back)?
Edited by FlatronEZ