TypeError: key(): Argument #1 ($array) must be of type array, null given in key()

I added this code inside `recurring_events\src\Plugin\FullcalendarViewProcessor\RecurringEventsFullCalendarProcessor.php` issue fixed

if (empty($variables['#attached']['drupalSettings']['fullCalendarView'])) {
      return;
    }

According to the error message, is it something from another module?

modules\contrib\recurring_events