Attempt to fix native crash in mapbox

I bet they don't like the view going away

app/src/main/java/com/geeksville/mesh/ui/MapFragment.kt

@@ -132,6 +132,7 @@ class MapFragment : ScreenFragment("Map"), Logging {
 
     var mapView: MapView? = null
 
+
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
@@ -141,8 +142,12 @@ class MapFragment : ScreenFragment("Map"), Logging {
             mapView = v
             v.onCreate(savedInstanceState)
 
+            mapView?.let { v ->
+                // Each time the pane is shown start fetching new map info (we do this here instead of
+                // onCreate because getMapAsync can die in native code if the view goes away)
                 v.getMapAsync { map ->
 
+                    if (view != null) { // it might have gone away by now
                         // val markerIcon = BitmapFactory.decodeResource(context.resources, R.drawable.ic_twotone_person_pin_24)
                         val markerIcon =
                             requireActivity().getDrawable(R.drawable.ic_twotone_person_pin_24)!!
@@ -155,6 +160,7 @@ class MapFragment : ScreenFragment("Map"), Logging {
                         }
 
                         model.nodeDB.nodes.observe(viewLifecycleOwner, Observer { nodes ->
+                            if (view != null)
                                 onNodesChanged(map, nodes.values)
                         })
 
@@ -163,6 +169,8 @@ class MapFragment : ScreenFragment("Map"), Logging {
                     }
                 }
             }
+        }
+    }
 
     override fun onPause() {
         mapView?.onPause()