Fix a crash when exiting the DevTools Connectivity page.

A lock was being released without checking if it was held, which
resulted in a crash because WifiManager.MulticastLock is reference
counted by default.

BUG=28668604

Change-Id: I306731129894d5525e974561c2680ae7db5aff4b

apps/Development/src/com/android/development/Connectivity.java

@@ -486,7 +486,9 @@ public class Connectivity extends Activity {
         mCm.unregisterNetworkCallback(mCallback);
         mCallback = null;
         unregisterReceiver(mReceiver);
-        mWml.release();
+        if (mWml.isHeld()) {
+            mWml.release();
+        }
     }
 
     @Override