Yeah, now I don't get that error anymore, I've got some other errors, probably only caused by my old this.send(client, message) functions. When I'm done upgrading all my code we'll know for sure, but for now it seems fixed. Thanks!
Edit:
Yeah, it's fixed. Thank you again!

Hello, I've upgraded colyseus from 0.12.x to 0.13 both on my game server and client (made with defold), now I'm getting this strange error as soon as I join the server:

Error

  DEBUG:SCRIPT: join error in chars_select: 
  DEBUG:SCRIPT: 
  { --[[000001A7D6D041C0]]
    code = 12,
    error = "ossil-"
  }

Generated by this code:

client:join_or_create("authroom", {username = username, password = password }, function(err, room2)
	if (err ~= nil) then
		print("join error in chars_select: ")
		pprint(err)
		return
	end
	isConnected = true
	room = room2
	return
end)

Then nothing happens until I close the client, and only in that moment, the server closes the Room.

I've tried to find some reference to this error code or description. The only thing I've found is that, maybe, 12 equals with "room left". I got it from github repo search, looking for "code 12".

Does anyone know what's happening to my game?
Thank you in advance!

Edit
could ossil be Fossil?