Use context for location provider if activity is not available

The current activity may be null when the location provider is created.
Use the React application context in that case.

android/src/main/java/com/github/reactnativecommunity/location/RNPlayServicesLocationProvider.java

@@ -46,8 +46,13 @@ public class RNPlayServicesLocationProvider implements RNLocationProvider {
 
     public RNPlayServicesLocationProvider(Activity activity, ReactApplicationContext context) {
         this.context = context;
-        locationProvider = LocationServices.getFusedLocationProviderClient(activity);
-        locationSettingsClient = LocationServices.getSettingsClient(activity);
+        if (activity != null) {
+            locationProvider = LocationServices.getFusedLocationProviderClient(activity);
+            locationSettingsClient = LocationServices.getSettingsClient(activity);
+        } else {
+            locationProvider = LocationServices.getFusedLocationProviderClient(context);
+            locationSettingsClient = LocationServices.getSettingsClient(context);
+        }
     }
 
     // Public interface