Ticket #31598: patch_31598.diff

cron.php

@@ -18 +18 @@
  * @param int $timestamp Timestamp for when to run the event.
  * @param string $hook Action hook to execute when cron is run.
  * @param array $args Optional. Arguments to pass to the hook's callback function.
+ *
+ * @return bool|null
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
         // don't schedule a duplicate if there's already an identical event due within 10 minutes of it
         $next = wp_next_scheduled($hook, $args);
         if ( $next && abs( $next - $timestamp ) <= 10 * MINUTE_IN_SECONDS ) {
-                return;
+                return null;
         }
 
         $crons = _get_cron_array();
@@ -46 +48 @@
         $crons[$event->timestamp][$event->hook][$key] = array( 'schedule' => $event->schedule, 'args' => $event->args );
         uksort( $crons, "strnatcasecmp" );
         _set_cron_array( $crons );
+
+        return true;
 }
 
 /**