From 7c47cdf16112ed6b15e8a918377156035a166f1e Mon Sep 17 00:00:00 2001
From: Simon Howard
Date: Tue, 26 Jan 2010 19:18:18 +0000
Subject: Fix glass hack windows where a linedef is flagged as two sided but
 has only one side. Fixes WADs such as OTTAWAU.WAD (thanks Never_Again).

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 1826
---
 src/p_sight.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'src/p_sight.c')

diff --git a/src/p_sight.c b/src/p_sight.c
index e192567b..79c1bb1d 100644
--- a/src/p_sight.c
+++ b/src/p_sight.c
@@ -173,7 +173,7 @@ boolean P_CrossSubsector (int num)
 	    continue;
 	
 	line->validcount = validcount;
-		
+
 	v1 = line->v1;
 	v2 = line->v2;
 	s1 = P_DivlineSide (v1->x,v1->y, &strace);
@@ -194,6 +194,14 @@ boolean P_CrossSubsector (int num)
 	if (s1 == s2)
 	    continue;	
 
+        // Backsector may be NULL if this is an "impassible
+        // glass" hack line.
+
+        if (line->backsector == NULL)
+        {
+            return false;
+        }
+
 	// stop because it is not two sided anyway
 	// might do this after updating validcount?
 	if ( !(line->flags & ML_TWOSIDED) )
-- 
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