Fixing crash in empty folders. (Bug 11627191)

Change-Id: I7a0e23e16a7546a9612d3406257e15be758d4c52
diff --git a/src/com/android/launcher3/LauncherModel.java b/src/com/android/launcher3/LauncherModel.java
index 74f28b3..a69617a 100644
--- a/src/com/android/launcher3/LauncherModel.java
+++ b/src/com/android/launcher3/LauncherModel.java
@@ -584,8 +584,9 @@
             // as in Workspace.onDrop. Here, we just add/remove them from the list of items
             // that are on the desktop, as appropriate
             ItemInfo modelItem = sBgItemsIdMap.get(itemId);
-            if (modelItem.container == LauncherSettings.Favorites.CONTAINER_DESKTOP ||
-                    modelItem.container == LauncherSettings.Favorites.CONTAINER_HOTSEAT) {
+            if (modelItem != null &&
+                    (modelItem.container == LauncherSettings.Favorites.CONTAINER_DESKTOP ||
+                     modelItem.container == LauncherSettings.Favorites.CONTAINER_HOTSEAT)) {
                 switch (modelItem.itemType) {
                     case LauncherSettings.Favorites.ITEM_TYPE_APPLICATION:
                     case LauncherSettings.Favorites.ITEM_TYPE_SHORTCUT: