Fix typo (thanks ExeterDad :)

init.lua

@@ -101,7 +101,7 @@ mobs:register_mob("mob_horse:horse", {
 				if inv:room_for_item("main", "mobs:saddle") then
 					inv:add_item("main", "mobs:saddle")
 				else
-					minetest.add_item(clicker.getpos(), "mobs:saddle")
+					minetest.add_item(clicker:getpos(), "mobs:saddle")
 				end
 
 			-- attach player to horse