Fix AppRTCDemo crash when room is connected after PC is destroyed.

webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java

Index: webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
diff --git a/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java b/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
index e2fa7d1e094ba2626d012d1e3d35a6569e5e5f9f..3073c34a9b7db5f57b89920df40dbe73a4b74cab 100644
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
@@ -369,7 +369,10 @@ public class CallActivity extends Activity
   private void callConnected() {
     final long delta = System.currentTimeMillis() - callStartedTimeMs;
     Log.i(TAG, "Call connected: delay=" + delta + "ms");
-
+    if (peerConnectionClient == null || isError) {
+      Log.w(TAG, "Call is connected in closed or error state");
+      return;
+    }
     // Update video view.
     updateVideoView();
     // Enable statistics callback.