I’m new to home assistant but i think this might be a bug regarding all configurations. I have the same promlem as you but also if I try the example configuration for Appdaamon i get the same error:
log_level: info
system_packages:
- ffmpeg
python_packages:
- PyMySQL
- Pillow
Edge: TypeError: Cannot read property ‘value’ of null
Mozilla: TypeError: this._editor is null