From affb984c5616537d2e9d63a3f93a9df8c8d7ec62 Mon Sep 17 00:00:00 2001
From: Wuzzy <Wuzzy2@mail.ru>
Date: Sat, 14 Dec 2019 01:30:21 +0100
Subject: [PATCH] Fix mapgen crash if there's unknown nodes

---
 mods/MAPGEN/mcl_mapgen_core/init.lua | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mods/MAPGEN/mcl_mapgen_core/init.lua b/mods/MAPGEN/mcl_mapgen_core/init.lua
index 3a4d972f9..4b65653db 100644
--- a/mods/MAPGEN/mcl_mapgen_core/init.lua
+++ b/mods/MAPGEN/mcl_mapgen_core/init.lua
@@ -1097,9 +1097,12 @@ local function generate_structures(minp, maxp, seed, biomemap)
 				local ground_y = nil
 				for y = struct_max, struct_min, -1 do
 					local checknode = minetest.get_node_or_nil({x=x,y=y,z=z})
-					if checknode and minetest.registered_nodes[checknode.name].walkable then
-						ground_y = y
-						break
+					if checknode then
+						local def = minetest.registered_nodes[checknode.name]
+						if def and def.walkable then
+							ground_y = y
+							break
+						end
 					end
 				end