fix header view issue

Author: hongxinhope

TBEmptyDataSet.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name         = "TBEmptyDataSet"
-  s.version      = "1.3"
+  s.version      = "1.4"
   s.summary      = "An extension of UITableView/UICollectionView's super class, it will display a placeholder when the data is empty."
 
   s.homepage     = "https://github.com/teambition/TBEmptyDataSet"

TBEmptyDataSet/TBEmptyDataSet.swift

@@ -243,8 +243,11 @@ extension UIScrollView: UIGestureRecognizerDelegate {
         emptyDataSetWillAppear()
 
         if emptyDataView.superview == nil {
-            addSubview(emptyDataView)
-            bringSubviewToFront(emptyDataView)
+            if (self is UITableView || self is UICollectionView) && subviews.count > 1 {
+                insertSubview(emptyDataView, atIndex: 0)
+            } else {
+                addSubview(emptyDataView)
+            }
         }
         emptyDataView.resetEmptyDataView()