Fix item count check in Folder#replaceFolderWithFinalItem()

Instead of checking the item count (number of views), check the number
of items in the model, since that is where the item is being removed.
This way, mInfo.contents.remove(0) will never be out of bounds.

Bug: 25666490
Change-Id: I0eb880b366157bddb5a8c342d538737722b7f0cd

src/com/android/launcher3/Folder.java

@@ -902,7 +902,6 @@ public class Folder extends LinearLayout implements DragSource, View.OnClickList
             // Show the animation, next time something is added to the folder.
             mInfo.setOption(FolderInfo.FLAG_MULTI_PAGE_ANIMATION, false, mLauncher);
         }
-
     }
 
     @Override
@@ -1122,7 +1121,7 @@ public class Folder extends LinearLayout implements DragSource, View.OnClickList
         Runnable onCompleteRunnable = new Runnable() {
             @Override
             public void run() {
-                int itemCount = getItemCount();
+                int itemCount = mInfo.contents.size();
                 if (itemCount <= 1) {
                     View newIcon = null;