Fix NullPointerException when connected but no video frame decoded

remoting/android/java/src/org/chromium/chromoting/DesktopView.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chromoting;
 
 import android.app.ActionBar;
 import android.app.Activity;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
@@ skipping 65 matching lines @@
      * cause the UI to lag. Specifically, it is currently invoked on the native
      * graphics thread using a JNI.
      */
     @Override
     public void run() {
         if (Looper.myLooper() == Looper.getMainLooper()) {
             Log.w("deskview", "Canvas being redrawn on UI thread");
         }
 
         Bitmap image = JniInterface.getVideoFrame();
+        if (image == null) {
+            // This can happen if the client is connected, but a complete video frame has not yet
+            // been decoded.
+            return;
+        }
 
         int width = image.getWidth();
         int height = image.getHeight();
         boolean sizeChanged = false;
         synchronized (mRenderData) {
             if (mRenderData.imageWidth != width || mRenderData.imageHeight != height) {
                 // TODO(lambroslambrou): Move this code into a sizeChanged() callback, to be
                 // triggered from JniInterface (on the display thread) when the remote screen size
                 // changes.
                 mRenderData.imageWidth = width;
@@ skipping 123 matching lines @@
     @Override
     public void showKeyboard() {
         // TODO(lambroslambrou): Implement this.
     }
 
     @Override
     public void transformationChanged() {
         requestRepaint();
     }
 }