From ef23b0e4ef1ea2b1458a585ef0119a05e29c3ac8 Mon Sep 17 00:00:00 2001
From: Andrew n marshall <Anm@anm.me>
Date: Fri, 13 Apr 2018 16:26:20 -0700
Subject: [PATCH] Do not reconnect a previous shadow block. Assume unplug()
 will recreate a new correct shadow.

---
 blocks/logic.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/blocks/logic.js b/blocks/logic.js
index 6b789db0a..15b08170f 100644
--- a/blocks/logic.js
+++ b/blocks/logic.js
@@ -542,14 +542,16 @@ Blockly.Constants.Logic.LOGIC_COMPARE_ONCHANGE_MIXIN = {
       var prevA = this.prevBlocks_[0];
       if (prevA !== blockA) {
         blockA.unplug();
-        if (prevA) {
+        if (prevA && !prevA.isShadow()) {
+          // The shadow block is automatically replaced during unplug().
           this.getInput('A').connection.connect(prevA.outputConnection);
         }
       }
       var prevB = this.prevBlocks_[1];
       if (prevB !== blockB) {
         blockB.unplug();
-        if (prevB) {
+        if (prevB && !prevB.isShadow()) {
+          // The shadow block is automatically replaced during unplug().
           this.getInput('B').connection.connect(prevB.outputConnection);
         }
       }