iOS App crashes if missing permissions for location updates

Our app was rejected by Apple because we had the background mode 'location updates' enabled, but we dont implemented a feature that would take use of it. The background mode with 'location updates' is required by the documentation of this plugin.

Because we dont use this feature in the background runner at all, we disabled the background mode. **This leads to an crashing background runner.**

We were able to modify the sourcecode of the background runner not using location at all. Now the app runs without crashes and without the backgroundmode 'location updates'.

This is a similar request to #86 which focuses Android. We would like to see more updates for the background runner; handling especially permissions.