Fix compile error

This commit fix the compile error when building Android
apk.

Author: splasky

example/lib/click_annotations.dart

@@ -80,8 +80,10 @@ class ClickAnnotationBodyState extends State<ClickAnnotationBody> {
   }
 
   Future<void> _onStyleLoaded() async {
-    await addImageFromAsset(
-        controller!, "custom-marker", "assets/symbols/custom-marker.png");
+    if (controller != null) {
+      await addImageFromAsset(
+          controller!, "custom-marker", "assets/symbols/custom-marker.png");
+    }
     controller!.addCircle(
       const CircleOptions(
         geometry: LatLng(-33.881979408447314, 151.171361438502117),

example/lib/layer.dart

@@ -145,11 +145,10 @@ class LayerState extends State {
     controller.onFeatureTapped.add(onFeatureTap);
   }
 
-  void onFeatureTap(
-      dynamic featureId, Point<double> point, LatLng latLng, String layerId) {
+  void onFeatureTap(dynamic featureId, Point<double> point, LatLng latLng) {
     final snackBar = SnackBar(
       content: Text(
-        'Tapped feature with id $featureId on layer $layerId',
+        'Tapped feature with id $featureId on layer',
         style: const TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
       ),
       backgroundColor: Theme.of(context).primaryColor,

example/lib/sources.dart

@@ -308,7 +308,9 @@ class FullMapState extends State<FullMap> {
 
   _onStyleLoadedCallback() async {
     final styleInfo = _stylesAndLoaders[selectedStyleId];
-    styleInfo.addDetails(controller!);
+    if (controller != null) {
+      styleInfo.addDetails(controller!);
+    }
     controller!
         .animateCamera(CameraUpdate.newCameraPosition(styleInfo.position));
   }