Invalid account causes app to crash 

Report from user:

```
If for some reason, the account set in the settings is no longer available, (like after a reïnstall of subsonic server)
The app will close/crash after startup. I cannot change the account because the app will close/crash before I can do anything.
The only solution is to remove the app, reïnstall it and set a new account. 
```
