Small refactor to separate adding workspace / all apps items

Change-Id: I06b7bc7f7f0e01696cb9670b8385e5148593e3e0
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index 709f4cf..f03ffc6 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -3844,15 +3844,17 @@
         }
 
         // Add the new screens
-        bindAddScreens(newScreens);
+        if (newScreens != null) {
+            bindAddScreens(newScreens);
+        }
 
         // We add the items without animation on non-visible pages, and with
         // animations on the new page (which we will try and snap to).
-        if (!addNotAnimated.isEmpty()) {
+        if (addNotAnimated != null && !addNotAnimated.isEmpty()) {
             bindItems(addNotAnimated, 0,
                     addNotAnimated.size(), false);
         }
-        if (!addAnimated.isEmpty()) {
+        if (addAnimated != null && !addAnimated.isEmpty()) {
             bindItems(addAnimated, 0,
                     addAnimated.size(), true);
         }