Query: Introduce an action which gets fired when a 404 is triggered.

Fixes #48061
Built from https://develop.svn.wordpress.org/trunk@47509


git-svn-id: http://core.svn.wordpress.org/trunk@47284 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-query.php

@@ -1711,6 +1711,15 @@ class WP_Query {
 		$this->is_404 = true;
 
 		$this->is_feed = $is_feed;
+
+		/**
+		 * Fires after a 404 is triggered.
+		 *
+		 * @since 5.5.0
+		 *
+		 * @param WP_Query $this The WP_Query instance (passed by reference).
+		 */
+		do_action_ref_array( 'set_404', array( $this ) );
 	}
 
 	/**

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47508';
+$wp_version = '5.5-alpha-47509';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.