From 52d801a06a804244292f4a872eeaf5e84a9f70b1 Mon Sep 17 00:00:00 2001
From: Ben Harris <bjh21@bjh21.me.uk>
Date: Fri, 31 Mar 2023 15:33:51 +0100
Subject: [PATCH] Require a grid description for hats grid

Without this, you can cause a null-pointer dereference by passing Loopy
a game description with no grid description, like "10x10t16:".
---
 grid.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/grid.c b/grid.c
index bac8be8..c2e08db 100644
--- a/grid.c
+++ b/grid.c
@@ -3496,6 +3496,9 @@ static const char *grid_validate_desc_hats(
     struct HatPatchParams hp;
     const char *error = NULL;
 
+    if (!desc)
+        return "Missing grid description string.";
+
     error = grid_desc_to_hat_params(desc, &hp);
     if (!error)
         error = hat_tiling_params_invalid(&hp);