Fix scroll bar in places picker

Summary: Changed the scroll bar from sorting by section when there is only one section

Test Plan: Ran unit tests, PlacePicker/FriendPicker/Scrumptious samples

Reviewers: jacl, clang, mmarucheck, gregschechte

Reviewed By: mmarucheck

CC: platform-diffs@lists, bhiller

Differential Revision: https://phabricator.fb.com/D541501

Task ID: 1235919

src/FBGraphObjectTableDataSource.m

@@ -418,7 +418,7 @@ - (NSInteger)tableView:(UITableView *)tableView
 
 - (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView
 {
-    return self.indexKeys;
+    return [self.indexKeys count] > 1 ? self.indexKeys : nil;
 }
 
 - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath