Fix crash when package list is updated

bug# 5224498

Change-Id: I8953589c21e97fee3f5c3b95fb4a46beb39562b3
diff --git a/src/com/android/launcher2/LauncherModel.java b/src/com/android/launcher2/LauncherModel.java
index 7d62062..4ad8922 100644
--- a/src/com/android/launcher2/LauncherModel.java
+++ b/src/com/android/launcher2/LauncherModel.java
@@ -605,9 +605,11 @@
             startLoaderFromBackground();
         } else if (SearchManager.INTENT_GLOBAL_SEARCH_ACTIVITY_CHANGED.equals(action) ||
                    SearchManager.INTENT_ACTION_SEARCHABLES_CHANGED.equals(action)) {
-            Callbacks callbacks = mCallbacks.get();
-            if (callbacks != null) {
-                callbacks.bindSearchablesChanged();
+            if (mCallbacks != null) {
+                Callbacks callbacks = mCallbacks.get();
+                if (callbacks != null) {
+                    callbacks.bindSearchablesChanged();
+                }
             }
         }
     }