src/Service/JobOrderHandler/CMBJobOrderHandler.php

@@ -544,6 +544,10 @@ class CMBJobOrderHandler implements JobOrderHandlerInterface
 
                     if (empty($rider)) {
                         $error_array['rider'] = 'Invalid rider specified.';
+                    } else {
+                        // check if rider is still available
+                        if (!($rider->isAvailable()))
+                            $error_array['rider'] = 'Selected rider is unavailable.';
                     }
                 }
             }