I am running a Minecraft server. I recently upgraded from 1.17-Pre2 to 1.17-Pre3. I copied over the server.properties file, op.json, whitelist.json, and banned*.json, and rhsmp/. The RHSMP is the world directory. This did not happen after I upgrades from Pre1 to Pre2 in the exact same way. Even though this is on Fabric, the same thing still happens when I try it with a pure vanilla server. Please note that neither the server nor the client logs a traceback.

After starting up Fabric (java jar fabric-server-launch.jar -nogui-), and trying to log in on my client, I get the following message:

Connection Lost

Interal Exception: io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Cannot invoke "na.b(String, int)" because "☃ is null

On the server-side (nothing above this is of any use):

[11:33:26] [Server thread/INFO]: Done (3.463s)! For help, type "help"
[11:33:26] [Server thread/INFO]: Starting remote control listener
[11:33:26] [Server thread/INFO]: Thread RCON Listener started
[11:33:26] [Server thread/INFO]: RCON running on 0.0.0.0:25575
[11:33:52] User Authenticator #1/INFO: UUID of player dellrium is aedb48d6-1423-4fe4-91d9-4d978030c2e8
[11:33:52] [Server thread/INFO]: dellrium[/67.172.252.125:34314] logged in with entity id 237 at (496.30000001192093, 70.5, -25.655683173746702)
[11:33:52] [Server thread/INFO]: dellrium joined the game
[11:33:53] [Server thread/INFO]: dellrium lost connection: Disconnected
[11:33:53] [Server thread/INFO]: dellrium left the game