From f9d7bc63bf55ed24239a784a15a04a27eca2f889 Mon Sep 17 00:00:00 2001
From: Brian Campbell <Brian.Campbell@ed.ac.uk>
Date: Sun, 26 Jun 2022 15:30:58 +0100
Subject: [PATCH] Fix underflow in free_window_info At the end this is called
 after `WIN_MESSAGE` is reset to `-1`, so we need a check here.

---
 win/tty/wintty.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/win/tty/wintty.c b/win/tty/wintty.c
index 0b5225c69..76443417e 100644
--- a/win/tty/wintty.c
+++ b/win/tty/wintty.c
@@ -1769,7 +1769,8 @@ free_window_info(struct WinDesc *cw, boolean free_data)
     int i;
 
     if (cw->data) {
-        if (cw == wins[WIN_MESSAGE] && cw->rows > cw->maxrow)
+        if (WIN_MESSAGE != WIN_ERR && cw == wins[WIN_MESSAGE]
+            && cw->rows > cw->maxrow)
             cw->maxrow = cw->rows; /* topl data */
         for (i = 0; i < cw->maxrow; i++)
             if (cw->data[i]) {