"Uninstall only" does not always work

Binary marker used to determine which kind of installer we are running (installer, updater, uninstaller... etc.) can be left in a wrong state when "Uninstall only" checkbox is checked in credentials page, causing wrong results.

Can be reproduced, for example by completing an update in maintenance tool and choosing restart in the final page, then check "Uninstall only", and binary marker is still set to updater.