Issue #3401849: Fix null sender error for Symfony Mailer

Closes #3401849

src/Email.php

@@ -469,7 +469,10 @@ class Email extends BaseEmail implements InternalEmailInterface {
     foreach ($this->addresses as $name => $addresses) {
       $value = [];
       foreach ($addresses as $address) {
-        $value[] = $address->getSymfony();
+        $email = $address->getEmail();
+        if (!empty($email)) {
+          $value[] = $address->getSymfony();
+        }
       }
       if ($value) {
         // Convert headers to camel case.