Comments: Restore inclusion of an empty comment type when building the `WHERE` clause in `WP_Comment_Query::get_comment_ids()`.

This ensures that `get_comments( array( 'type' => 'comment' ) )` still includes comments that have not yet migrated to the `comment` type.

Follow-up to [47597].

Props ocean90.
See #49236.
Built from https://develop.svn.wordpress.org/trunk@47625


git-svn-id: http://core.svn.wordpress.org/trunk@47400 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-comment-query.php

@@ -741,6 +741,7 @@ class WP_Comment_Query {
 
 					case 'comment':
 					case 'comments':
+						$comment_types[ $operator ][] = "''";
 						$comment_types[ $operator ][] = "'comment'";
 						break;
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47623';
+$wp_version = '5.5-alpha-47625';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.