tlwebadm calls rrdtool to generate the license graphs. This call rarely goes wrong, but there could be bugs that cause it to fail. Unfortunately we don't deal with these failures properly.
The code assumes that rrdtool will return with a non-zero error code. Unfortunately it never does that.
The code also assumes it will get an error message on stdout, but rrdtool writes the error on stderr. We don't redirect stderr, which means it ends up in the log file without any formatting:
> ERROR: unknown option '--border'
> 2023-01-30 15:21:37 INFO tlwebadm: [::ffff:10.47.1.240] 'GET /status/viewlicenses?days=1&width=640&height=400 HTTP/1.1' 200 -