Avoids java.lang.NullPointerException in WebRtcAudioRecord

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioRecord.java

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 87 matching lines @@
         if (DEBUG) {
           long nowTime = System.nanoTime();
           long durationInMs =
               TimeUnit.NANOSECONDS.toMillis((nowTime - lastTime));
           lastTime = nowTime;
           Logging.d(TAG, "bytesRead[" + durationInMs + "] " + bytesRead);
         }
       }
 
       try {
-        audioRecord.stop();
+        if (audioRecord != null) {
+          audioRecord.stop();
+        }
       } catch (IllegalStateException e) {
         Logging.e(TAG, "AudioRecord.stop failed: " + e.getMessage());
       }
     }
 
     // Stops the inner thread loop and also calls AudioRecord.stop().
     // Does not block the calling thread.
     public void stopThread() {
       Logging.d(TAG, "stopThread");
       keepAlive = false;
@@ skipping 165 matching lines @@
 
   private native void nativeDataIsRecorded(int bytes, long nativeAudioRecord);
 
   // Sets all recorded samples to zero if |mute| is true, i.e., ensures that
   // the microphone is muted.
   public static void setMicrophoneMute(boolean mute) {
      Logging.w(TAG, "setMicrophoneMute(" + mute + ")");
     microphoneMute = mute;
   }
 }