1. access the zul page in the browser.
2. close node 1.
3. upload an image.
it will cause nullpoint execption
Problem accessing session data : class
java.lang.NullPointerException null

<zk>
<zscript>
void upload(UploadEvent event) {
org.zkoss.util.media.Media media = event.getMedia();
if (media instanceof org.zkoss.image.Image)

{ org.zkoss.zul.Image image = new org.zkoss.zul.Image(); image.setContent( (org.zkoss.image.Image) media); image.setParent(pics); }

else

{ Messagebox.show("Not an image: "+media, "Error", Messagebox.OK, Messagebox.ERROR); }

}
</zscript>
<button label="Upload" upload="true" onUpload="upload(event)"/>
<toolbarbutton label="Upload" upload="true" onUpload="upload(event)"/>
<vbox id="pics" />
</zk>