Safari mac: fix scrolling

fix #1562
* changed to use document.scrollingElement
as topmost element, which seem correct and required by safari.

Author: adumesny

doc/CHANGES.md

@@ -57,7 +57,8 @@ Change log
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 ## 4.2.1-dev
 
-- fix [#1684](https://github.com/gridstack/gridstack.js/issues/1684) mac Safari H5 draggable broken in 4.0.1. Thanks [@wurambo](https://github.com/wurambo)
+- fix [#1684](https://github.com/gridstack/gridstack.js/issues/1684) [#1550](https://github.com/gridstack/gridstack.js/issues/1550) mac Safari H5 draggable broken in 4.0.1. Thanks [@wurambo](https://github.com/wurambo)
+- fix [#1562](https://github.com/gridstack/gridstack.js/issues/1562) mac Safari page scroll fix
 
 ## 4.2.1 (2021-4-18)
 

src/utils.ts

@@ -293,7 +293,7 @@ export class Utils {
 
   /** @internal */
   static getScrollParent(el: HTMLElement): HTMLElement {
-    if (el === null) return document.documentElement;
+    if (el === null) return document.scrollingElement as HTMLElement;
     const style = getComputedStyle(el);
     const overflowRegex = /(auto|scroll)/;