Fix issue where you could page to -1 during spring loaded drag (issue 10640529)

Change-Id: I487c871af4ec4412ee4edc74ce58947e54ccd43b
diff --git a/src/com/android/launcher3/Workspace.java b/src/com/android/launcher3/Workspace.java
index 4dca599..9dfe18b 100644
--- a/src/com/android/launcher3/Workspace.java
+++ b/src/com/android/launcher3/Workspace.java
@@ -2951,6 +2951,11 @@
         float smallestDistSoFar = Float.MAX_VALUE;
 
         for (int i = 0; i < screenCount; i++) {
+            // The custom content screen is not a valid drag over option
+            if (mScreenOrder.get(i) == CUSTOM_CONTENT_SCREEN_ID) {
+                continue;
+            }
+
             CellLayout cl = (CellLayout) getChildAt(i);
 
             final float[] touchXy = {originX, originY};