Fix issue w/ the_post_navigation

Hey,

just found that when using single post navigation on singular items, the title is removed there as well which is sure not intended.

I’d recommend to fix it like this in your the_title hook:

	// only remove title for the target post
	// fixes issues w/ the_post_navigation()
	if( $post_id !== get_the_ID() ) {
		return $title;
	}