**System Information**
Operating system: Linux-5.8.7-arch1-1-x86_64-with-arch 64 Bits
Graphics card: GeForce GTX 660M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.66
**Blender Version**
Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-11-05 22:40, hash: `rB02677ec4e0fa`
Worked: 2.90
Caused by {rB4b20eebb85cc}
--> apparently the Addon misused the API though, so needs changes in the Addon
**Addon Information**
Name: Icon Viewer (1, 4, 0)
Author: roaoao
**Short description of error**
The button on the python console header is missing.
**Exact steps for others to reproduce the error**
* Enable the Icon Viewer addon.
* Make sure the Show Header preference is enabled (it's on by default).
* Switch the Timeline editor to a Console editor.
* Observe the missing button.