I am new to wordpress and was encountered the Warning: Undefined array key 5408 in C:\xampp\htdocs\Bridge\wp-includes\nav-menu-template.php on line 210, is there any solution for me to fix this issue?

I just set up a wordpress website with 150 posts of a custom post type. On the single pages of each post, I want to have a “Previous” and “Next” to let readers read more post on my ...