get_adjacent_post generates invalid query for custom post types that don't support categories

[batmoo]

If a custom post type isn't registered against the category taxonomy, setting $in_same_cat results in an invalid query.

SELECT p.* FROM wp_posts AS p
INNER JOIN wp_term_relationships AS tr ON p.ID = tr.object_id
INNER JOIN wp_term_taxonomy tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
AND tt.taxonomy = 'category'
AND tt.term_id IN ()
WHERE p.post_date > '2012-05-15 16:15:07'
AND p.post_type = 'book'
AND p.post_status = 'publish'
AND tt.taxonomy = 'category'
ORDER BY p.post_date ASC LIMIT 1

Quick and dirty test code:

add_action( 'init', function() {
        register_post_type( 'book', array( 'label' => 'Books', 'public' => true ) );
});

add_action( 'template_redirect', function() {
        if ( is_singular( 'book' ) )
                var_dump( get_adjacent_post( true, '', false ) );
} );

[SergeyBiryukov]

#15959