From 78f0bbf9fab92cbeceaa7a2cff14109d8e642838 Mon Sep 17 00:00:00 2001
From: Louis Moureaux <m_louis30@yahoo.com>
Date: Wed, 27 Dec 2023 01:55:11 +0100
Subject: [PATCH] Fix crash in layer_terrain

Check that there is a group before trying to dereference it. The user may not
have provided one.

Closes #2017.
---
 client/tileset/layer_terrain.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/client/tileset/layer_terrain.cpp b/client/tileset/layer_terrain.cpp
index d781f2f08d..2fb4da25f0 100644
--- a/client/tileset/layer_terrain.cpp
+++ b/client/tileset/layer_terrain.cpp
@@ -786,7 +786,12 @@ int layer_terrain::terrain_group(const terrain *pterrain) const
     return -1;
   }
 
-  return m_terrain_info.at(terrain_index(pterrain)).group->number;
+  auto group = m_terrain_info.at(terrain_index(pterrain)).group;
+  if (!group) {
+    return -1;
+  }
+
+  return group->number;
 }
 
 namespace /* anonymous */ {