keditfiletype: fix crash when adding apps to "empty" views
thou shalt not c-cast => let's dynamic cast, through dynamic cast we'll notice that the items aren't actually what we thought they should be and then we can skip them.
notably when there is no app association we insert a fake 'None' entry, this entry is still present when updatePreferredServices runs but needs skipping because it does not represent a service
I should note that the UX for the new-association use case is fairly buggy still, but at least it doesn't crash