fix(rest-api): handle null in prepare_items_query()

Use null coalescing to default to an empty array
instead of wrapping the loop in an is_array() check
in WP_REST_Posts_Controller and
WP_REST_Revisions_Controller.

Author: apermo

src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -1210,7 +1210,8 @@ public function delete_item( $request ) {
 	 * @return array Items query arguments.
 	 */
 	protected function prepare_items_query( $prepared_args = array(), $request = null ) {
-		$query_args = array();
+		$query_args    = array();
+		$prepared_args = $prepared_args ?? array();
 
 		foreach ( $prepared_args as $key => $value ) {
 			/**

src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php

@@ -548,7 +548,8 @@ public function delete_item( $request ) {
 	 * @return array Items query arguments.
 	 */
 	protected function prepare_items_query( $prepared_args = array(), $request = null ) {
-		$query_args = array();
+		$query_args    = array();
+		$prepared_args = $prepared_args ?? array();
 
 		foreach ( $prepared_args as $key => $value ) {
 			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php */