a listbox without ROD causes a websocket connection to close

Steps to Reproduce

1. run the attached zul with WebSocket enabled

Current Result

a dialog shows:
the server is temporarily out of service.
would you like to try again?

Expected Result

no such dialog

Debug Information

zWs.Manager
onClose: function onClose(reason) {}
set log point in onCloset to print reason,
CloseEvent {isTrusted: true, wasClean: true, code: 1009, reason: 'The decoded text message was too big for the output buffer and the endpoint does not support partial messages',

Workaround

• set a bigger buffer size, see WebSocketEndPoint.java

Proposed solution

• library property to set websocket buffer size
• show a precise error message(failure reason) when this kind of error happens