From 15635ec7c82e1dfa7a1fe70bb2931ce7defd6352 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Fri, 11 Jun 2021 23:18:46 +0200
Subject: [PATCH] - fixed crash when trying to triangulate broken sectors.

In these cases it is possible that the wall index may go below 0.
---
 source/core/sectorgeometry.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/core/sectorgeometry.cpp b/source/core/sectorgeometry.cpp
index 801c7889e..ec6131442 100644
--- a/source/core/sectorgeometry.cpp
+++ b/source/core/sectorgeometry.cpp
@@ -241,7 +241,7 @@ bool SectorGeometry::MakeVertices(unsigned int secnum, int plane, const FVector2
 		int start = 0;
 		while (done[start] && start < numvertices) start++;
 		int s = start;
-		if (start < numvertices)
+		if (start >= 0 && start < numvertices)
 		{
 			while (!done[start])
 			{