502 error when adding custom post archive item in menu

Hi.
Thank You for your plugin. But it have a small bug.
When adding menu item for custom post archive, appearing the error in web console.
It happens during saving current menu item.
For fix this bug I added inspection for current post type. If it is ‘nav_menu_item’ when return false.

In daves-wordpress-live-search.php I added

if ('nav_menu_item' == $post->post_type)
	        return false;

in updateFirstImagePostmeta function.
Please,fix this in next version.