[BUGFIX] Solved error while upgrading from 2.1 to 2.2

Given error while running setup:upgrade:

	`postcode is a required field`

Problem is solved by setting tax_postcode to * if it was NULL

Author: lewisvoncken

app/code/Magento/Tax/Setup/UpgradeData.php

@@ -91,6 +91,9 @@ public function upgrade(ModuleDataSetupInterface $setup, ModuleContextInterface
                     /** @var \Magento\Directory\Model\Region $region */
                     $region = $this->directoryRegionFactory->create();
                     $region->loadByCode($regionCode, $taxRateData->getTaxCountryId());
+                    if ($taxRateData->getTaxPostcode() === null) {
+                        $taxRateData->setTaxPostcode('*');
+                    }
                     $taxRateData->setTaxRegionId($region->getRegionId());
                     $this->taxRateRepository->save($taxRateData);
                 }