[google_maps_flutter] fixed a small bug in example app. (#3590)

in _onMarkerTapped function we were changing markers[markerId] to defaultMarker and than again markers[markerId] to hueGreen marker, while instead we should have changed markers[selectedMarker] to defaultMarker first instead of markers[markerId]

Author: vishnuagbly

packages/google_maps_flutter/google_maps_flutter/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.0.0-nullsafety.1
+
+* Fix in example app to properly change marker icon.
+
 ## 2.0.0-nullsafety
 
 * Migrate to null-safety

packages/google_maps_flutter/google_maps_flutter/example/lib/place_marker.dart

@@ -53,10 +53,11 @@ class PlaceMarkerBodyState extends State<PlaceMarkerBody> {
     final Marker? tappedMarker = markers[markerId];
     if (tappedMarker != null) {
       setState(() {
-        if (markers.containsKey(markerId)) {
-          final Marker resetOld = markers[markerId]!
+        final MarkerId? previousMarkerId = selectedMarker;
+        if (previousMarkerId != null && markers.containsKey(previousMarkerId)) {
+          final Marker resetOld = markers[previousMarkerId]!
               .copyWith(iconParam: BitmapDescriptor.defaultMarker);
-          markers[markerId] = resetOld;
+          markers[previousMarkerId] = resetOld;
         }
         selectedMarker = markerId;
         final Marker newMarker = tappedMarker.copyWith(

packages/google_maps_flutter/google_maps_flutter/pubspec.yaml

@@ -1,7 +1,7 @@
 name: google_maps_flutter
 description: A Flutter plugin for integrating Google Maps in iOS and Android applications.
 homepage: https://github.com/flutter/plugins/tree/master/packages/google_maps_flutter/google_maps_flutter
-version: 2.0.0-nullsafety
+version: 2.0.0-nullsafety.1
 
 dependencies:
   flutter: