[android] fix source ownership

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/CannotAddSourceException.java

@@ -0,0 +1,12 @@
+package com.mapbox.mapboxsdk.style.sources;
+
+/**
+ * Thrown when adding a source to a map twice
+ */
+public class CannotAddSourceException extends RuntimeException {
+
+    public CannotAddSourceException(String message) {
+        super(message);
+    }
+
+}