Fix NPE due to delayed event handling.

a.k.a., annoying monkeys.

Bug: 6336430
Change-Id: Ie038a71d0ae66b3f30ccd704529f767fa2058542

src/com/android/settings/wifi/WifiSettings.java

@@ -527,6 +527,9 @@ public class WifiSettings extends SettingsPreferenceFragment
      * the strength of network and the security for it.
      */
     private void updateAccessPoints() {
+        // Safeguard from some delayed event handling
+        if (getActivity() == null) return;
+
         final int wifiState = mWifiManager.getWifiState();
 
         switch (wifiState) {