Allow the expiration date to be set to null

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

apps/sharebymail/lib/ShareByMailProvider.php

@@ -370,14 +370,14 @@ class ShareByMailProvider implements IShareProvider {
 	 * @param string $link
 	 * @param string $initiator
 	 * @param string $shareWith
-	 * @param \DateTime $expiration
+	 * @param \DateTime|null $expiration
 	 * @throws \Exception If mail couldn't be sent
 	 */
 	protected function sendMailNotification($filename,
 											$link,
 											$initiator,
 											$shareWith,
-											\DateTime $expiration) {
+											$expiration) {
 		$initiatorUser = $this->userManager->get($initiator);
 		$initiatorDisplayName = ($initiatorUser instanceof IUser) ? $initiatorUser->getDisplayName() : $initiator;
 		$subject = (string)$this->l->t('%s shared »%s« with you', array($initiatorDisplayName, $filename));

apps/sharebymail/tests/ShareByMailProviderTest.php

@@ -868,6 +868,7 @@ class ShareByMailProviderTest extends TestCase {
 				'https://example.com/file.txt',
 				'OwnerUser',
 				'john@doe.com',
+				null,
 			]);
 	}
 
@@ -968,6 +969,7 @@ class ShareByMailProviderTest extends TestCase {
 				'https://example.com/file.txt',
 				'InitiatorUser',
 				'john@doe.com',
+				null,
 			]);
 	}
 }