MC-39483: Impossible to delete region from customer address via import

- fixed
- modified test

Author: Oleksandr Dubovyk

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

@@ -645,7 +645,7 @@ protected function _prepareDataForUpdate(array $rowData): array
                 $value = $rowData[$attributeAlias];
 
                 if (!strlen($rowData[$attributeAlias])) {
-                    if (!$newAddress) {
+                    if ($attributeParams['is_required']) {
                         continue;
                     }
 

dev/tests/integration/testsuite/Magento/CustomerImportExport/Model/Import/AddressTest.php

@@ -80,7 +80,7 @@ class AddressTest extends TestCase
         'remove' => [ // this data is not set in CSV file
             '19107' => [
                 'city' => 'Philadelphia',
-                'region' => 'Pennsylvania',
+                'region' => null,
             ],
         ],
         'default' => [ // new default billing/shipping addresses
@@ -568,9 +568,10 @@ public function testUpdateFirstAndLastName()
         $this->assertEquals($address->getStreet(), $updatedAddress->getStreet());
         $this->assertEquals($address->getCity(), $updatedAddress->getCity());
         $this->assertEquals($address->getCountryId(), $updatedAddress->getCountryId());
-        $this->assertEquals($address->getPostcode(), $updatedAddress->getPostcode());
         $this->assertEquals($address->getTelephone(), $updatedAddress->getTelephone());
         $this->assertEquals($address->getRegionId(), $updatedAddress->getRegionId());
+        //assert empty non-required values changed
+        $this->assertEquals(null, $updatedAddress->getPostcode());
     }
 
     /**