Minimserver 2 docker on synology : license file has zero length

[Fredowulf]

Hello,
Congratulations for this software.
I'd like to use it on docker, for stability reasons. I had trouble this afternoon related to java 8 corrupted installation, that was painful. Thus, docker.
I followed the tutorial on minimserver website, using 2.0.16 first then 2.0.18 version : both of them gave me an error message, "license file has zero length". The same error persists when connecting to the website (x.x.x.x:9790).
I specified puid and pgid, but the error was still there.
I hope I didn't kill two licenses trying to use docker...
Do someone has an idea ?
Regards,
F.