Fix NPE

Bug: 7357742
Change-Id: I4d12d137b9d5ebf5c6739cbd4405de3f90a3d846

Author: isheriff

wifi/java/android/net/wifi/WifiManager.java

@@ -1983,7 +1983,9 @@ public void captivePortalCheckComplete() {
 
     protected void finalize() throws Throwable {
         try {
-            mHandler.getLooper().quit();
+            if (mHandler != null && mHandler.getLooper() != null) {
+                mHandler.getLooper().quit();
+            }
         } finally {
             super.finalize();
         }