Micro-optimize validation of empty email addresses

Then we don't have to construct any validators.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

lib/private/Mail/Mailer.php

@@ -221,6 +221,10 @@ class Mailer implements IMailer {
 	 * @return bool True if the mail address is valid, false otherwise
 	 */
 	public function validateMailAddress(string $email): bool {
+		if ($email === '') {
+			// Shortcut: empty addresses are never valid
+			return false;
+		}
 		$validator = new EmailValidator();
 		$validation = new RFCValidation();
 

tests/lib/Mail/MailerTest.php

@@ -178,6 +178,7 @@ class MailerTest extends TestCase {
 			['lukas@192.168.1.1', true],
 			['lukas@éxämplè.com', true],
 			['asdf', false],
+			['', false],
 			['lukas@owncloud.org@owncloud.com', false],
 		];
 	}