Steps to Reproduce

• Create a PDF page with a big image in it (so that loading this data takes a long time)
• Open the PDF in the PDF viewer component
• Close the PDF viewer before the loading of the page is complete

Current Result

JavaScript error "Cannot read property 'lastChild' of undefined"

Expected Result

The PDF viewer in the browser should cancel pending requests or silently swallow them.

Debug Information

The affected compoent is org.zkoss.zkex.zul.Pdfviewer

Workaround

Haven't found one, yet