From ebdf3865d4dc17b0bb885f10fb36f517c2b9ba73 Mon Sep 17 00:00:00 2001
From: "Michael \"Z\" Goddard" <mzgoddard@gmail.com>
Date: Fri, 19 Apr 2019 15:50:44 -0400
Subject: [PATCH] retire new threads if they have no block after the hat

---
 src/engine/sequencer.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/engine/sequencer.js b/src/engine/sequencer.js
index 464cd7489..61a758f0a 100644
--- a/src/engine/sequencer.js
+++ b/src/engine/sequencer.js
@@ -177,6 +177,12 @@ class Sequencer {
         if (!currentBlockId) {
             // A "null block" - empty branch.
             thread.popStack();
+
+            // Did the null follow a hat block?
+            if (thread.stack.length === 0) {
+                thread.status = Thread.STATUS_DONE;
+                return;
+            }
         }
         // Save the current block ID to notice if we did control flow.
         while ((currentBlockId = thread.peekStack())) {