Fix muspostbossname sometimes returning garbage.

src/p_setup.c

@@ -355,8 +355,8 @@ static void P_ClearSingleMapHeaderInfo(INT16 i)
 	mapheaderinfo[num]->mustrack = 0;
 	mapheaderinfo[num]->muspos = 0;
 	mapheaderinfo[num]->musinterfadeout = 0;
-	mapheaderinfo[num]->musintername[0] = '\0';
-	mapheaderinfo[num]->muspostbossname[6] = 0;
+	mapheaderinfo[num]->musintername[0] = 0;
+	mapheaderinfo[num]->muspostbossname[0] = 0;
 	mapheaderinfo[num]->muspostbosstrack = 0;
 	mapheaderinfo[num]->muspostbosspos = 0;
 	mapheaderinfo[num]->muspostbossfadein = 0;