Steps to Reproduce

run ZK using CE or PE

trigger an event to server:

<button onClick=""/>

Current Result

zk.wpd:formatted:12597 Uncaught ReferenceError: zWs is not defined
    at Object.sendNow (zk.wpd:formatted:12597)
    at zk.wpd:formatted:12267

Expected Result

no error

Root Cause

incorrect checks for undefined variables
e.g.:
https://github.com/zkoss/zk/blob/6b4ae14a691e663ab8199e4315aeb4c662544b56/zk/src/archive/web/js/zk/au.js#L712