Steps to Reproduce

1. run the attached file
2. upload a text file

Current Result

java.lang.IllegalStateException: Use getStringData() instead
at org.zkoss.util.media.AMedia.newIllegalStateException(AMedia.java:358)
at org.zkoss.util.media.AMedia.getByteData(AMedia.java:313)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)

Expected Result

uploaded successfully

Debug Information

• 8.5.0 doesn't have such issue
• sent request is: http://localhost:8080/zk8support/zkau/dropupload?uuid=lW2Q2&dtid=z_gvo&native=undefined

  zk.UploadUtils = {
  	ajaxUpload: function (wgt, xhr, formData) {
  		var dt = wgt.desktop,
  			tempUri = zk.ajaxURI('/dropupload', {desktop: dt,au: true}),
  			ajaxUri = tempUri + (tempUri.indexOf('?') == -1 ? '?' : '&')
  				+ 'uuid=' + wgt.uuid
  				+ '&dtid=' + dt.id
  				+ '&native=' + wgt._native;
  
  

  wgt._native is undefined

• a client widget should not send natvie which is a parameter specified at upload attribute.