Can't hide courtesy key signature if key changes to C major / A minor
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 18.104.22.1681459983, revision: 465e7b6
See attached score. In measure 9, since the change is to no key signature (C major etc.), there is no right-click menu from which to hide the courtesy key sig.