Fix a crash on some devices when launching the widget configuration

Change-Id: I810ce18d52f851344e7309d57fc1a460f153e2c8
diff --git a/src/com/android/contacts/widget/PinnedHeaderListView.java b/src/com/android/contacts/widget/PinnedHeaderListView.java
index 5936002..a533927 100644
--- a/src/com/android/contacts/widget/PinnedHeaderListView.java
+++ b/src/com/android/contacts/widget/PinnedHeaderListView.java
@@ -296,6 +296,7 @@
         ensurePinnedHeaderLayout(viewIndex);
 
         View child = getChildAt(position - getFirstVisiblePosition());
+        if (child == null) return;
 
         PinnedHeader header = mHeaders[viewIndex];
         header.visible = true;