@Simon thanks again for reporting the error. I'll see if I can reproduce it. It looks like it's in the Home Assistant integration. Sorry about the trouble.
EDIT: I see from your screenshot that this.computer_name was null for some reason, so I added code to prevent a crash when that happens. I'll produce a new version soon.
https://github.com/rvmey/TRIGGERcmd-Agent/commit/b54e988e7d251105bc6faa8c3fa6a5240644cbef
EDIT2: Done - please upgrade to the current version (v1.0.52) to avoid that error in the future.