Fix world_id packet handling

[turikhay]

This should now work with any server implementation of world_id channel

[Brokkonaut]

Hi, I would like to have 2 changes to this pr:

For the received packets: Currently it is not required to send a 42 at all, and not all server implementations send that (some just send a 0). So i would recommend the following for legacy compatibility:

• read the first byte and ignore it
• read the second byte
• if the second byte is 42 read another byte for the length, otherwise accept the second byte as length
• read the world name

So it should accept all fixed packets and the old ones if the world name does not have 42 bytes (and as that is a quite long name, it should probably not happen)

For the sent packets: Here it should be fine if just the "fixed" packet is sent, because most implementations ignore the content anyways.