Steps to Reproduce

The issue occurs only when using the Dropupload component with websockets and having pending events to be sent to the server, for example if you previously clicked on the textbox component of the Dropupload.

Current Result

The selected document content is sent via POST with other events accumulated that weren't sent inmediately but they're encoded allowing empty fields so eventually it fails on the server side class AuMultipartUploader::splitQueryParameter generating this stacktrace (and failing to upload the document):

java.lang.NullPointerException: Cannot invoke "String.length()" because "s" is null java.base/java.net.URLDecoder.decode(URLDecoder.java:173) java.base/java.net.URLDecoder.decode(URLDecoder.java:138) org.zkoss.zk.au.http.AuMultipartUploader.splitQueryParameter(AuMultipartUploader.java:188) java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:215) java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:1024) java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570) java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560) java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921) java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265) java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:727) org.zkoss.zk.au.http.AuMultipartUploader.splitQuery(AuMultipartUploader.java:177) org.zkoss.zk.au.http.AuMultipartUploader$AuMultipartDecoder.<init>(AuMultipartUploader.java:301) org.zkoss.zk.au.http.AuMultipartUploader.parseRequest(AuMultipartUploader.java:166) org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:452) org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:408) org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:416)

Expected Result

Debug Information

Workaround

I have temporarily solved the issue with this workaround that ensures that there's no empty field

 
zk.afterLoad('zkmax', function () {
var xZWs = {};
zk.override(zkmax.websocket_.zWs, xZWs, {
encode: function (j, aureq, dt) {
var content = {},
opts = aureq.opts || {},
target = aureq.target;
content['dtid'] = dt.id;
content["cmd_".concat(j)] = aureq.name;
if ((opts.implicit || opts.ignorable) && !opts.serverAlive) content["opt_".concat(j)] = 'i';
if (target && target.className !== 'zk.Desktop') content["uuid_".concat(j)] = target.uuid;
var data = aureq.data;
if (typeof data === 'string' || typeof data === 'number' || typeof data === 'boolean' || Array.isArray(data)) data =

;
if (data) content["data_".concat(j)] = zAu.toJSON(target, data);
return content;
}
}); //zk.override
});//zk.afterLoad