Ticket #15959: get_adjacent_post.patch

wp-includes/link-template.php

@@ -1110 +1110 @@
 
                 if ( $in_same_cat ) {
                         $cat_array = wp_get_object_terms($post->ID, 'category', array('fields' => 'ids'));
-                        $join .= " AND tt.taxonomy = 'category' AND tt.term_id IN (" . implode(',', $cat_array) . ")";
+                        if( !empty( $cat_array ) )
+                                $join .= " AND tt.taxonomy = 'category' AND tt.term_id IN (" . implode(',', $cat_array) . ")";
                 }
 
                 $posts_in_ex_cats_sql = "AND tt.taxonomy = 'category'";