XML-RPC: Make sure editing a draft post with `wp.editPost` does not unintentionally cause its published date to be set.

Props redsweater.
Fixes #45322.
Built from https://develop.svn.wordpress.org/trunk@45906


git-svn-id: http://core.svn.wordpress.org/trunk@45717 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-xmlrpc-server.php

@@ -1708,6 +1708,16 @@ class wp_xmlrpc_server extends IXR_Server {
 			$post['post_date_gmt'] = $this->_convert_date( $post['post_date_gmt'] );
 		}
 
+		/*
+		 * If the API client did not provide post_date, then we must not perpetuate the value that was
+		 * stored in the database, or it will appear to be an intentional edit. Conveying it here as if
+		 * it was coming from the API client will cause an otherwise zeroed out post_date_gmt to get set
+		 * with the value that was originally stored in the database when the draft was created.
+		 */
+		if ( ! isset( $content_struct['post_date'] ) ) {
+			unset( $post['post_date'] );
+		}
+
 		$this->escape( $post );
 		$merged_content_struct = array_merge( $post, $content_struct );
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45905';
+$wp_version = '5.3-alpha-45906';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.