Limit casket spawns.

abms.lua

@@ -302,7 +302,19 @@ minetest.register_abm({
 	nodenames = {"fun_caves:casket"},
 	interval = 2,
 	chance = 10,
-	action = function(pos, node)
+	catch_up = false,
+	action = function(pos, node, aoc, active_object_count_wider)
+		-- do not spawn if too many active entities in area
+		if active_object_count_wider > 5 then
+			return
+		end
+
+		local meta = minetest.get_meta(pos)
+		local ready = meta:get_string('formspec')
+		if ready ~= '' then
+			return
+		end
+
 		local objs = minetest.get_objects_inside_radius(pos, 7)
 		for i = 1, #objs do
 			if objs[i]:is_player() then