QClipboard doesn't detect loss of clipboard in another application (X11)

Steps to reproduce:

• compile and run the attached test app
• open another X11 application (KWrite, XTerm, whatever can set clipboard/selection)
• Ctrl+C or mouse select to create new clipboard/selection content in that application
• test app notifies about the change
• close the application owning the clipboard/selection content
• test app does not notify about the change

Expected results:

• test app notifies about the change in the last step