From 93b66ff8daae6de46438672464e6b35b021452ae Mon Sep 17 00:00:00 2001
From: Pasi Kallinen <paxed@alt.org>
Date: Fri, 23 Jul 2021 21:09:35 +0300
Subject: [PATCH] Prevent segfault on nonexistent mapseen

Cannot happen on normal play, but with some lua trickery ...
---
 src/dungeon.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/dungeon.c b/src/dungeon.c
index 5f851a0a7..9bf9343e6 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -3000,6 +3000,8 @@ mapseen_temple(struct monst *priest UNUSED) /* currently unused;
 {
     mapseen *mptr = find_mapseen(&u.uz);
 
+    if (!mptr)
+        return;
     if (Is_valley(&u.uz))
         mptr->flags.valley = 1;
     else if (Is_sanctum(&u.uz))
@@ -3012,7 +3014,8 @@ room_discovered(int roomno)
 {
     mapseen *mptr = find_mapseen(&u.uz);
 
-    mptr->msrooms[roomno].seen = 1;
+    if (mptr)
+        mptr->msrooms[roomno].seen = 1;
 }
 
 /* #overview command */