[android] - load style without url or json

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapboxMap.java

@@ -837,7 +837,7 @@ public final class MapboxMap {
       nativeMapView.setStyleJson(builder.getJson());
     } else {
       // user didn't provide a `from` component, load a blank style instead
-      nativeMapView.setStyleJson("{}");
+      nativeMapView.setStyleJson(Style.EMPTY_JSON);
     }
   }
 

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/Style.java

@@ -37,6 +37,8 @@ import java.util.Map;
 @SuppressWarnings("unchecked")
 public class Style {
 
+  static final String EMPTY_JSON = "{\"version\": 8,\"sources\": {},\"layers\": []}";
+
   private final NativeMap nativeMap;
   private final HashMap<String, Source> sources = new HashMap<>();
   private final HashMap<String, Layer> layers = new HashMap<>();