The client-side handler for entity attribute data currently has an error which will cause exceptions to be thrown in a situation where this is most likely not intended to happen.
Using MCP names, the relevant function is NetHandlerPlayClient.handleEntityProperties (handler for this client-bound packet), which has the following block of code:
While this appears to be intended to register a dummy attribute instance for any unknown attribute data recieved, the RangedAttribute created here is invalid and will cause an IllegalArgumentException to be thrown by the constructor:
This is because the minimum value specified is greater than the default of 0. The correct minimum value should probably be -Double.MAX_VALUE instead of Double.MIN_NORMAL, as negative values are allowed here (e.g. generic.luck).