From a6b0734fe814425d2d3638e313b3102327064185 Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Tue, 11 Jan 2022 08:11:36 -0800
Subject: [PATCH] Prevent exception being thrown in reflow smaller

Fixes #3602
---
 src/common/buffer/Buffer.ts | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/common/buffer/Buffer.ts b/src/common/buffer/Buffer.ts
index c788bf36..f927cc8e 100644
--- a/src/common/buffer/Buffer.ts
+++ b/src/common/buffer/Buffer.ts
@@ -367,6 +367,11 @@ export class Buffer implements IBuffer {
       let srcCol = lastLineLength;
       while (srcLineIndex >= 0) {
         const cellsToCopy = Math.min(srcCol, destCol);
+        if (wrappedLines[destLineIndex] === undefined) {
+          // Sanity check that the line exists, this has been known to fail for an unknown reason
+          // which would stop the reflow from happening if an exception would throw.
+          break;
+        }
         wrappedLines[destLineIndex].copyCellsFrom(wrappedLines[srcLineIndex], srcCol - cellsToCopy, destCol - cellsToCopy, cellsToCopy, true);
         destCol -= cellsToCopy;
         if (destCol === 0) {