Save only valid D-Bus Names

[JakobDev]

Flatpak has a Bug that Apps didn't start when you give them Permission to talk to a invalid D-Dbus name (flatpak/flatpak#4940). Until this is fixed, it is better to block writing invalid D-Bus names. If someone does accidental use a invalid D-Bus name for global and ignore the warning, no Flatpak App will start until the problem is solved with the Flatpak cli or the overrides file is deleted.