Steps to Reproduce

1. Run with Keikai component

Current Result

zss.wpd:30290 Uncaught ReferenceError: SimpleBar is not defined

Expected Result

No error at all

Debug Information

zk.wpd in Keikai component with browser condition won't work with ZK 10

<script src="ext/simplebar.js" browser="gecko,safari,opera,chrome,ios,android,edge"/> 

Because of this commit https://github.com/zkoss/zk/blob/5c4aadeb4b4a2b5bf12d32de48aec149b693a542/zk/src/main/java/org/zkoss/zk/ui/http/WpdExtendlet.java#L899

If sourceMapManager is null, it won't do anything.

Workaround

None.