Don't abort when merely checking if a non-map is a map

- When P_OpenMapData() is called by P_CheckMapData(), we don't actually
  care if any required lumps are missing. This just means it isn't a valid
  map, so don't abort with I_Error().

src/compatibility.cpp

@@ -541,7 +541,7 @@ CCMD (mapchecksum)
 	}
 	for (int i = 1; i < argv.argc(); ++i)
 	{
-		map = P_OpenMapData(argv[i]);
+		map = P_OpenMapData(argv[i], true);
 		if (map == NULL)
 		{
 			Printf("Cannot load %s as a map\n", argv[i]);

src/g_level.cpp

@@ -1923,7 +1923,7 @@ CCMD(listmaps)
 	for(unsigned i = 0; i < wadlevelinfos.Size(); i++)
 	{
 		level_info_t *info = &wadlevelinfos[i];
-		MapData *map = P_OpenMapData(info->mapname);
+		MapData *map = P_OpenMapData(info->mapname, true);
 
 		if (map != NULL)
 		{

src/p_setup.cpp

@@ -250,7 +250,7 @@ static int GetMapIndex(const char *mapname, int lastindex, const char *lumpname,
 //
 //===========================================================================
 
-MapData *P_OpenMapData(const char * mapname)
+MapData *P_OpenMapData(const char * mapname, bool justcheck)
 {
 	MapData * map = new MapData;
 	FileReader * wadReader = NULL;
@@ -331,13 +331,18 @@ MapData *P_OpenMapData(const char * mapname)
 					const char * lumpname = Wads.GetLumpFullName(lump_name + i);
 					try
 					{
-						index = GetMapIndex(mapname, index, lumpname, true);
+						index = GetMapIndex(mapname, index, lumpname, !justcheck);
 					}
 					catch(...)
 					{
 						delete map;
 						throw;
 					}
+					if (index == -2)
+					{
+						delete map;
+						return NULL;
+					}
 					if (index == ML_BEHAVIOR) map->HasBehavior = true;
 
 					// The next lump is not part of this map anymore
@@ -471,13 +476,18 @@ MapData *P_OpenMapData(const char * mapname)
 			{
 				try
 				{
-					index = GetMapIndex(maplabel, index, lumpname, true);
+					index = GetMapIndex(maplabel, index, lumpname, !justcheck);
 				}
 				catch(...)
 				{
 					delete map;
 					throw;
 				}
+				if (index == -2)
+				{
+					delete map;
+					return NULL;
+				}
 				if (index == ML_BEHAVIOR) map->HasBehavior = true;
 
 				// The next lump is not part of this map anymore
@@ -508,7 +518,7 @@ MapData *P_OpenMapData(const char * mapname)
 
 bool P_CheckMapData(const char *mapname)
 {
-	MapData *mapd = P_OpenMapData(mapname);
+	MapData *mapd = P_OpenMapData(mapname, true);
 	if (mapd == NULL) return false;
 	delete mapd;
 	return true;
@@ -3610,7 +3620,7 @@ void P_SetupLevel (char *lumpname, int position)
 	P_FreeLevelData ();
 	interpolator.ClearInterpolations();	// [RH] Nothing to interpolate on a fresh level.
 
-	MapData *map = P_OpenMapData(lumpname);
+	MapData *map = P_OpenMapData(lumpname, true);
 	if (map == NULL)
 	{
 		I_Error("Unable to open map '%s'\n", lumpname);

src/p_setup.h

@@ -94,7 +94,7 @@ struct MapData
 	void GetChecksum(BYTE cksum[16]);
 };
 
-MapData * P_OpenMapData(const char * mapname);
+MapData * P_OpenMapData(const char * mapname, bool justcheck);
 bool P_CheckMapData(const char * mapname);
 
 

src/statistics.cpp

@@ -463,7 +463,7 @@ void STAT_ChangeLevel(const char *newl)
 		{
 			// we reached the end of this episode
 			int wad = 0;
-			MapData * map = P_OpenMapData(StartEpisode->mEpisodeMap);
+			MapData * map = P_OpenMapData(StartEpisode->mEpisodeMap, false);
 			if (map != NULL)
 			{
 				wad = Wads.GetLumpFile(map->lumpnum);