Extra error checking.

fortress.lua

@@ -89,7 +89,15 @@ newnode.description = "Treasure Chest"
 newnode.on_construct = nil
 newnode.drop = 'default:chest'
 newnode.on_rightclick = function(pos, node, clicker, itemstack, pointed_thing)
+	if not pos then
+		return
+	end
+
 	local meta = minetest.get_meta(pos)
+	if not meta then
+		return
+	end
+
 	local ready = meta:get_string('formspec')
 	if ready == '' then
 		local level = math.max(6, math.ceil(pos.y / math.floor(max_depth / 6)))
@@ -123,6 +131,10 @@ function table.shuffle(self)
 end
 
 function unionfind(max)
+	if not (max and type(max) == 'number') then
+		return
+	end
+
 	local u = { _parent = {}, _rank = {} }
 
 	for i = 0, max-1 do
@@ -164,6 +176,10 @@ end
 
 
 local function maze_floor(y2, minp, maxp, data, area, node)
+	if not (y2 and minp and maxp and data and area and node and type(y2) == 'number' and type(data) == 'table') then
+		return
+	end
+
 	-- walls is zero-based.
 	local walls = {}
 	for i = 0, 2 * cells * cells - 1 do
@@ -290,7 +306,12 @@ local designs = {
 		{0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0},
 	},
 }
+
 local function design_floor(y2, minp, maxp, data, area, node)
+	if not (y2 and minp and maxp and data and area and node and type(y2) == 'number' and type(data) == 'table') then
+		return
+	end
+
 	local design = designs[math.random(#designs)]
 
 	local py = minp.y + y2 * cell_size
@@ -341,6 +362,10 @@ end
 
 
 fun_caves.fortress = function(minp_in, maxp_in, data, area, node)
+	if not (minp_in and maxp_in and data and area and node and type(data) == 'table') then
+		return
+	end
+
 	-- hungry maze
 	-- chests (w traps)
 	-- step traps (math based)
@@ -357,6 +382,9 @@ fun_caves.fortress = function(minp_in, maxp_in, data, area, node)
 	local treasure_count = 0
 	local csize = vector.add(vector.subtract(maxp_in, minp_in), 1)
 	local floor_1 = minetest.get_perlin_map(floor_noise_1, {x=csize.x, y=csize.z}):get2dMap_flat({x=minp_in.x, y=minp_in.z})
+	if not floor_1 then
+		return
+	end
 
 	for y2 = 0, cells-1 do
 		local floor_type = math.random(20)