Happens with or without Resource pack "Eureka! Create Airships!" but only in creative mode. I had the RP installed at first, the game crashed, removed the RP and started client again, it crashed.

I'm using the code from browse example (https://github.com/eclipse/milo/blob/master/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client ...