Fix crash when changing level size

mods/lzr_levels/init.lua

@@ -222,9 +222,17 @@ end
 -- 	Either one of these (or none of them for empty room):
 --	 	- level: level ID (for builtin level)
 -- 		- schematic: Path to schematic
--- 	- nodes: Table containing:
+-- 	- nodes (optional): Table containing node names of level border nodes:
 -- 		- node_floor, node_ceiling, node_wall, node_window
 function lzr_levels.build_room(room_data)
+	if not room_data.nodes then
+		room_data.nodes = {
+			node_floor = FLOOR_NODE,
+			node_wall = WALL_NODE,
+			node_ceiling = CEILING_NODE,
+			node_window = WINDOW_NODE,
+		}
+	end
 	prepare_room(room_data)
 end
 
@@ -239,12 +247,6 @@ function lzr_levels.prepare_and_build_level(level, spawn_pos, yaw)
 end
 
 function lzr_levels.prepare_and_build_custom_level(schematic, spawn_pos, yaw)
-	local nodes = {
-		node_floor = FLOOR_NODE,
-		node_wall = WALL_NODE,
-		node_ceiling = CEILING_NODE,
-		node_window = WINDOW_NODE,
-	}
 	lzr_levels.build_room({pos=lzr_globals.LEVEL_POS, size=schematic.size, schematic=schematic, spawn_pos=spawn_pos, yaw=yaw, nodes=nodes})
 end