Hide scroll bar if recycler view has no items.

Bug: 185873180
Test: Manually tested
Change-Id: Id0b21b264417aff19cfdcb46228bb497310ccc1b
diff --git a/src/com/android/launcher3/widget/picker/WidgetsRecyclerView.java b/src/com/android/launcher3/widget/picker/WidgetsRecyclerView.java
index b016b4f..d9861be 100644
--- a/src/com/android/launcher3/widget/picker/WidgetsRecyclerView.java
+++ b/src/com/android/launcher3/widget/picker/WidgetsRecyclerView.java
@@ -116,6 +116,7 @@
     public void onUpdateScrollbar(int dy) {
         // Skip early if widgets are not bound.
         if (isModelNotReady()) {
+            mScrollbar.setThumbOffsetY(-1);
             return;
         }