Make sure mService exists when we call start or stop

[ivosabev]

This handles the crash where mService has been killed or not initialized at all and the stop() method is called on a null value.

Examples:

Fatal Exception: java.lang.NullPointerException
Attempt to invoke virtual method 'void com.marianhello.bgloc.LocationService.start()' on a null object reference
com.marianhello.bgloc.BackgroundGeolocationFacade.startBackgroundService

Unable to destroy activity {com.xxx.yyy/com.xxx.yyy.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.marianhello.bgloc.LocationService.stop()' on a null object reference
android.app.ActivityThread.performDestroyActivity

[mauron85]

Ok, thanks. It will be merged. However this is just fixing symptoms. Fundamental question is why mService becomes null.

[ivosabev]

I haven't got to time extensively test what exactly causes this, but I think it is because the current code doesn't account about the fact that the service could stop unexpectedly between the BackgroundGeolocationFacade.stop() call and the actual BackgroundGeolocationFacade. stopBackgroundService() meaning that onServiceDisconnected() might be called and the service could become null.

Also it is not accounted about the fact that binder.getService() might return null in onServiceConnected(). For example in the BackgroundGeolocationFacade.stop() you check for mService being null, but still call the stopBackgroundService() even if it is null.

[mauron85]

Merged. Thanks.