From 2e2a5c230e1d84439c687a597cf7b26dfc7f15d6 Mon Sep 17 00:00:00 2001
From: Beka Westberg <bekawestberg@gmail.com>
Date: Wed, 19 Aug 2020 13:21:44 -0700
Subject: [PATCH] Fix lastMarker_ disposal (#4184)

---
 core/insertion_marker_manager.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/core/insertion_marker_manager.js b/core/insertion_marker_manager.js
index 2d47dd296..bf7c8ae3e 100644
--- a/core/insertion_marker_manager.js
+++ b/core/insertion_marker_manager.js
@@ -306,6 +306,14 @@ Blockly.InsertionMarkerManager.prototype.initAvailableConnections_ = function()
   if (lastOnStack && lastOnStack != this.topBlock_.nextConnection) {
     available.push(lastOnStack);
     this.lastOnStack_ = lastOnStack;
+    if (this.lastMarker_) {
+      Blockly.Events.disable();
+      try {
+        this.lastMarker_.dispose();
+      } finally {
+        Blockly.Events.enable();
+      }
+    }
     this.lastMarker_ = this.createMarkerBlock_(lastOnStack.getSourceBlock());
   }
   return available;