/usr/share/applications/qemu.desktop should have an "Exec=" key.

This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1868221
Reported by 'Lockywolf' on 2020-03-20 :

According to the www.freedesktop.org .desktop-file specification, all
"Application" desktop files should have an "Exec=" key. The one in qemu
doesn't.

This can be easily verified by running kbuildsycoca4 if KDE4 is present,
but the issue is not DE-dependent.

Which binary exactly should be assigned as the default one, I don't know.