QuicChannelBootstrap requires handler != null or streamHandler != null, seems unecessary.

[hirshi001]

Like the title says, in QuicChannelBootstrap::connect there is the following check

public Future<QuicChannel> connect(Promise<QuicChannel> promise) {
        if (handler == null && streamHandler == null) {
            throw new IllegalStateException("handler and streamHandler not set");
        }

This check doesn't seem to make sense, why is it only an illegal state if both handler and streamHandler are null? What about if only one was null?

Also, why would it matter if either of them is null, as a handler can always be added to the pipeline after creation?

[normanmaurer]

This basically mimics what we also do in netty for TCP where we require a handler