Clipboard cannot be changed from compositor if client has copied something

To reproduce, run attached compositor (minimal-cpp) and start the client application. Press "copy" button, then wait until the compositor tries to do overrideSelection()+updateSelection() (does so every 10 seconds).

QClipboard::changed is emitted, but the data available through QClipboard does not change.

It only starts working again if the mimeData is cleared from QClipboard.