chore(demo): Initialize map fragment when map ID is null

Allows the demo application to run even when a map ID is not provided by instantiating the `SupportMapFragment` without `GoogleMapOptions`.

Author: dkhawk

demo/src/main/java/com/google/maps/android/utils/demo/BaseDemoActivity.java

@@ -97,18 +97,19 @@ private void setUpMap(Bundle savedInstanceState) {
         // 2. Call the getMapId() method
         String mapId = app.getMapId();
 
+        // Create a new SupportMapFragment instance
+        SupportMapFragment mapFragment;
+
         if (mapId == null) {
-            finish();  // Note the main application will inform the user of the need for the map ID.
-            return;
+            mapFragment = SupportMapFragment.newInstance();
+        } else {
+            // Create the map options
+            GoogleMapOptions mapOptions = new GoogleMapOptions();
+            mapOptions.mapId(mapId);
+            // Create a new SupportMapFragment instance
+            mapFragment = SupportMapFragment.newInstance(mapOptions);
         }
 
-        // Create the map options
-        GoogleMapOptions mapOptions = new GoogleMapOptions();
-        mapOptions.mapId(mapId);
-
-        // Create a new SupportMapFragment instance
-        SupportMapFragment mapFragment = SupportMapFragment.newInstance(mapOptions);
-
         // Add the fragment to the container (R.id.map)
         // Check savedInstanceState to prevent re-adding on rotation
         if (savedInstanceState == null) {