Fix NPE in releaseMediaRecorder. do not merge

Change-Id: I3b96bbaf3889ebf0ce825a20337196df04f11d19
diff --git a/src/com/android/camera/VideoCamera.java b/src/com/android/camera/VideoCamera.java
index 48ffea6..ee05f9e 100644
--- a/src/com/android/camera/VideoCamera.java
+++ b/src/com/android/camera/VideoCamera.java
@@ -1037,8 +1037,9 @@
             mMediaRecorder.release();
             mMediaRecorder = null;
         }
-        // Take back the camera object control from media recorder.
-        mCameraDevice.lock();
+        // Take back the camera object control from media recorder. Camera
+        // device may be null if the activity is paused.
+        if (mCameraDevice != null) mCameraDevice.lock();
     }
 
     private void createVideoPath() {