Cron: Prevent sending headers when using ALTERNATE_WP_CRON

ALTERNATE_WP_CRON echos things which causes a "Headers already sent" warning. This adds a check to ensure headers haven't already been sent.

Previously: [45560]

See: #45560. Fixes #48283.
Props dlh.


Built from https://develop.svn.wordpress.org/trunk@46458


git-svn-id: http://core.svn.wordpress.org/trunk@46256 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-cron.php

@@ -20,8 +20,11 @@ ignore_user_abort( true );
 
 /* Don't make the request block till we finish, if possible. */
 if ( function_exists( 'fastcgi_finish_request' ) && version_compare( phpversion(), '7.0.16', '>=' ) ) {
+	if ( ! headers_sent() ) {
 		header( 'Expires: Wed, 11 Jan 1984 05:00:00 GMT' );
 		header( 'Cache-Control: no-cache, must-revalidate, max-age=0' );
+	}
+
 	fastcgi_finish_request();
 }
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-beta3-46457';
+$wp_version = '5.3-beta3-46458';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.