avoid setting order state to NULL (#778)

This may happen when setting a status that is not default for a state.
Fixes Adyen/adyen-magento2#384
Co-authored-by: Attila Kiss <42297201+cyattilakiss@users.noreply.github.com>

Model/Cron.php

@@ -1945,7 +1945,6 @@ class Cron
     {
         $statusObject = $this->_orderStatusCollection->create()
             ->addFieldToFilter('main_table.status', $status)
-            ->addFieldToFilter('state_table.is_default', true)
             ->joinStates()
             ->getFirstItem();