Audio wave overview not empty when recording silent

[inl1ne]

If the loopback test records nothing (because, for instance, the loopback adapter is broken) then the little overview wave in the top right hand corner shows some kind of default wave that looks legit. That's confusing because it at first appears that the recording succeeded. Recording failure should clear that overview box so it's more obvious that we recorded silence.

[gkasten]

I agree, the error handling could be improved.