ACP2E-356: Cannot create a new customer from Admin if Customer Sharing setting is set to Global

- Reverting old fix for allowing blank storeview to be saved in Send Welcome Email From field.

Author: Mohan Ahuja

app/code/Magento/Customer/Controller/Adminhtml/Index/Save.php

@@ -349,7 +349,7 @@ public function execute()
                     ['customer' => $customer, 'request' => $this->getRequest()]
                 );
 
-                if (isset($customerData['sendemail_store_id']) && !empty($customerData['sendemail_store_id'])) {
+                if (isset($customerData['sendemail_store_id']) && $customerData['sendemail_store_id'] !== false) {
                     $customer->setStoreId($customerData['sendemail_store_id']);
                     try {
                         $this->customerAccountManagement->validateCustomerStoreIdByWebsiteId($customer);