From 1080252504e6fc6c331dd4d686ca6f4026bb7837 Mon Sep 17 00:00:00 2001
From: Kevin Cooper <cooperka92@gmail.com>
Date: Thu, 1 Aug 2019 15:18:53 -0700
Subject: [PATCH] Fail with better error when thread not found

---
 packages/botkit/src/conversation.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/botkit/src/conversation.ts b/packages/botkit/src/conversation.ts
index 0450f7198..3cde0277a 100644
--- a/packages/botkit/src/conversation.ts
+++ b/packages/botkit/src/conversation.ts
@@ -574,6 +574,10 @@ export class BotkitConversation<O extends object = {}> extends Dialog<O> {
         // Let's interpret the current line of the script.
         const thread = this.script[step.thread];
 
+        if (!thread) {
+            throw new Error(`Thread '${step.thread}' not found, did you add any messages to it?`)
+        }
+
         // Capture the previous step value if there previous line included a prompt
         var previous = (step.index >= 1) ? thread[step.index - 1] : null;
         if (step.result && previous && previous.collect) {