Fixed yard signs being able to overwrite other nodes

signs_lib.lua

@@ -144,6 +144,11 @@ minetest.register_node(":default:sign_wall", {
 				itemstack:take_item()
 				return itemstack
 		elseif wdir == 1 then
+            local def = minetest.registered_nodes[minetest.env:get_node(pointed_thing.above).name]
+            if homedecor_node_is_owned(pointed_thing.above, placer)
+             or (not def.buildable_to) then
+                return
+            end
 		    minetest.env:add_node(above, {name = "signs:sign_yard", param2 = fdir})
 		    sign_info = signs_yard[fdir + 1]
 		else