[android][v10] Add guard to prevent NRE on map.getStyle().styleLayers (rnmapbox#3595)

* Add guard to prevent NRE crashing android apps on launch of map without styleLayers being a valid array

* Update android/src/main/java/com/rnmapbox/rnmbx/components/mapview/RNMBXMapView.kt

Use early return instead of optional chaining an iterator.

Co-authored-by: Miklós Fazekas <mfazekas@szemafor.com>

---------

Co-authored-by: Frederick Engelhardt <fre@vllc.dev>
Co-authored-by: Miklós Fazekas <mfazekas@szemafor.com>

Author: FrederickEngelhardt

android/src/main/java/com/rnmapbox/rnmbx/components/mapview/RNMBXMapView.kt

@@ -1129,8 +1129,15 @@ open class RNMBXMapView(private val mContext: Context, var mManager: RNMBXMapVie
             Logger.e("MapView", "setSourceVisibility, map is null")
             return
         }
-        val style = mMap!!.getStyle();
-        style!!.styleLayers.forEach {
+        val style = mMap.getStyle();
+
+        val styleLayers = style?.styleLayers
+        if (styleLayers == null) {
+            Logger.e("MapView", "setSourceVisibility, map.getStyle().styleLayers is null")
+            return
+        }
+
+        styleLayers.forEach {
             val layer = style.getLayer(it.id)
             if ((layer != null) && match(layer, sourceId, sourceLayerId)) {
                 layer.visibility(