Fix scope for visualizer object release

// ----------------------------------------------------------------------------

static void android_media_visualizer_native_release(JNIEnv *env,  jobject thiz) {

    { //limit scope so that lpVisualizer is deleted before JNI storage data.

        sp<Visualizer> lpVisualizer = setVisualizer(env, thiz, 0);

        if (lpVisualizer == 0) {

            return;

        }

    }

    // delete the JNI data

    VisualizerJniStorage* lpJniStorage =

        (VisualizerJniStorage *)env->GetLongField(thiz, fields.fidJniData);