How to fix the «Undefined index: amasty_ogrid_base_subtotal» error in the Amasty's «Extended Order Grid» module?

Notice: Undefined index: amasty_ogrid_base_subtotal in vendor/magento/module-sales/Ui/Component/Listing/Column/Price.php on line 55


How to fix

Locate the method \Amasty\Ogrid\Plugin\OrderDataProvider::afterGetSearchResult().
Replace its last line from

return $collection;


return $collection->clear();


The method tries to modify an SQL (particularly, to add the amasty_ogrid_base_subtotal column to the SQL) for an already loaded collection, but Magento ignores it because the collection is already loaded and cached.
To apply a collection’s SQL modifications we need to call the clear() method on it.