Android: Guard against switching camera on stopped camera

talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java

Index: talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java
diff --git a/talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java b/talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java
index aeb5418f75451c571a87fe1a4ffd7c094a8ccd35..5962e5585be17f7c18baa832b689e5f73a551b12 100644
--- a/talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java
+++ b/talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java
@@ -168,9 +168,9 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     if (Camera.getNumberOfCameras() < 2 )
       return false;
 
-    if (cameraThread == null) {
-      Log.e(TAG, "Camera has not been started");
-      return false;
+    if (cameraThreadHandler == null) {
+        Log.e(TAG, "Calling switchCamera() for stopped camera.");
+        return false;
     }
     if (pendingCameraSwitch) {
       // Do not handle multiple camera switch request to avoid blocking