Set fallback values for email and _website columns to avoid 'undefined index' error in CustomerComposite.php

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Author: TomashKhamlai

app/code/Magento/CustomerImportExport/Model/Import/CustomerComposite.php

@@ -299,8 +299,8 @@ public function validateData()
         $rows = [];
         foreach ($source as $row) {
             $rows[] = [
-                Address::COLUMN_EMAIL => $row[Customer::COLUMN_EMAIL],
-                Address::COLUMN_WEBSITE => $row[Customer::COLUMN_WEBSITE],
+                Address::COLUMN_EMAIL => $row[Customer::COLUMN_EMAIL] ?? null,
+                Address::COLUMN_WEBSITE => $row[Customer::COLUMN_WEBSITE] ?? null
             ];
         }
         $source->rewind();