Fixed a potential null pointer in filter list refresh receiver

astrid/src/com/todoroo/astrid/activity/FilterListFragment.java

@@ -543,7 +543,9 @@ public class FilterListFragment extends ListFragment {
             if(intent == null || !AstridApiConstants.BROADCAST_EVENT_REFRESH.equals(intent.getAction()))
                 return;
 
-            getActivity().runOnUiThread(new Runnable() {
+            Activity activity = getActivity();
+            if (activity != null) {
+                activity.runOnUiThread(new Runnable() {
                     @Override
                     public void run() {
                         refresh();
@@ -551,4 +553,5 @@ public class FilterListFragment extends ListFragment {
                 });
             }
         }
+    }
 }