fix: Ensure `label` is always a string

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

apps/files_sharing/lib/Controller/ShareAPIController.php

@@ -740,7 +740,10 @@ class ShareAPIController extends OCSController {
 			}
 
 			// If we have a label, use it
-			if (!empty($label)) {
+			if ($label !== '') {
+				if (strlen($label) > 255) {
+					throw new OCSBadRequestException('Maximum label length is 255');
+				}
 				$share->setLabel($label);
 			}
 

apps/sharebymail/lib/ShareByMailProvider.php

@@ -1008,7 +1008,7 @@ class ShareByMailProvider extends DefaultShareProvider implements IShareProvider
 		$share->setPassword($data['password']);
 		$passwordExpirationTime = \DateTime::createFromFormat('Y-m-d H:i:s', $data['password_expiration_time'] ?? '');
 		$share->setPasswordExpirationTime($passwordExpirationTime !== false ? $passwordExpirationTime : null);
-		$share->setLabel($data['label']);
+		$share->setLabel($data['label'] ?? '');
 		$share->setSendPasswordByTalk((bool)$data['password_by_talk']);
 		$share->setHideDownload((bool)$data['hide_download']);
 		$share->setReminderSent((bool)$data['reminder_sent']);

lib/private/Share20/Share.php

@@ -66,14 +66,13 @@ class Share implements IShare {
 	private $shareTime;
 	/** @var bool */
 	private $mailSend;
-	/** @var string */
-	private $label = '';
 	/** @var ICacheEntry|null */
 	private $nodeCacheEntry;
 	/** @var bool */
 	private $hideDownload = false;
 	private bool $reminderSent = false;
 
+	private string $label = '';
 	private bool $noExpirationDate = false;
 
 	public function __construct(