- Fixed crash on maps with out of range sidedef and sector numbers, a…

…dapted from PRBoom.

src/maploader/maploader.cpp

@@ -1702,13 +1702,6 @@ void MapLoader::LoadLineDefs (MapData * map)
 		}
 		else
 		{
-			// patch missing first sides instead of crashing out.
-			// Visual glitches are better than not being able to play.
-			if (LittleShort(mld->sidenum[0]) == NO_INDEX)
-			{
-				Printf("Line %d has no first side.\n", i);
-				mld->sidenum[0] = 0;
-			}
 			sidecount++;
 			if (LittleShort(mld->sidenum[1]) != NO_INDEX)
 				sidecount++;
@@ -1747,6 +1740,22 @@ void MapLoader::LoadLineDefs (MapData * map)
 			ProcessEDLinedef(ld, mld->tag);
 		}
 #endif
+		// cph 2006/09/30 - fix sidedef errors right away.
+		for (int j=0; j < 2; j++)
+		{
+			if (LittleShort(mld->sidenum[j]) != NO_INDEX && mld->sidenum[j] >= Level->sides.Size())
+			{
+				mld->sidenum[j] = 0; // dummy sidedef
+				Printf("Linedef %d has a bad sidedef\n", i);
+			}
+		}
+		// patch missing first sides instead of crashing out.
+		// Visual glitches are better than not being able to play.
+		if (LittleShort(mld->sidenum[0]) == NO_INDEX)
+		{
+			Printf("Line %d has no first side.\n", i);
+			mld->sidenum[0] = 0;
+		}
 
 		ld->v1 = &Level->vertexes[LittleShort(mld->v1)];
 		ld->v2 = &Level->vertexes[LittleShort(mld->v2)];
@@ -2180,11 +2189,11 @@ void MapLoader::LoadSideDefs2 (MapData *map, FMissingTextureTracker &missingtex)
 		// killough 4/4/98: allow sidedef texture names to be overloaded
 		// killough 4/11/98: refined to allow colormaps to work as wall
 		// textures if invalid as colormaps but valid as textures.
-
+		// cph 2006/09/30 - catch out-of-range sector numbers; use sector 0 instead
 		if ((unsigned)LittleShort(msd->sector)>=Level->sectors.Size())
 		{
 			Printf (PRINT_HIGH, "Sidedef %d has a bad sector\n", i);
-			sd->sector = sec = nullptr;
+			sd->sector = sec = &Level->sectors[0];
 		}
 		else
 		{