From d3256e621bb43a537213ffcd86b10dc0bd070c0b Mon Sep 17 00:00:00 2001
From: Artur Arseniev <artur.catch@hotmail.it>
Date: Thu, 19 Nov 2020 14:04:46 +0100
Subject: [PATCH] Prevent frame scroll on the first component drag. Fixes #3134

---
 src/canvas/view/FrameView.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/canvas/view/FrameView.js b/src/canvas/view/FrameView.js
index ab01e1e34..6d8afa2de 100644
--- a/src/canvas/view/FrameView.js
+++ b/src/canvas/view/FrameView.js
@@ -1,5 +1,5 @@
 import Backbone from 'backbone';
-import { bindAll, isString, debounce } from 'underscore';
+import { bindAll, isString, debounce, isUndefined } from 'underscore';
 import CssRulesView from 'css_composer/view/CssRulesView';
 import ComponentView from 'dom_components/view/ComponentView';
 import {
@@ -162,11 +162,12 @@ export default Backbone.View.extend({
 
   autoscroll() {
     if (this.dragging) {
+      const { lastClientY } = this;
       const canvas = this.em.get('Canvas');
       const win = this.getWindow();
       const body = this.getBody();
       const actualTop = body.scrollTop;
-      const clientY = this.lastClientY || 0;
+      const clientY = lastClientY || 0;
       const limitTop = canvas.getConfig().autoscrollLimit;
       const limitBottom = this.getRect().height - limitTop;
       let nextTop = actualTop;
@@ -180,6 +181,7 @@ export default Backbone.View.extend({
       }
 
       if (
+        !isUndefined(lastClientY) && // Fixes #3134
         nextTop !== actualTop &&
         nextTop > 0 &&
         nextTop < this.lastMaxHeight