fix(profile): fix getUID on nullable user variable

As per method signature, $visitingUser is nullable, so we can't be sure calling getUid() on it will
work.

Closes #35766

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/private/Profile/ProfileManager.php

@@ -168,7 +168,7 @@ private function registerAction(ILinkAction $action, IUser $targetUser, ?IUser $
 				return;
 			}
 			if (!$this->appManager->isEnabledForUser($action->getAppId(), $visitingUser)) {
-				$this->logger->notice('App: ' . $action->getAppId() . ' cannot register actions as it is not enabled for the visiting user: ' . $visitingUser->getUID());
+				$this->logger->notice('App: ' . $action->getAppId() . ' cannot register actions as it is not enabled for the visiting user: ' . ($visitingUser ? $visitingUser->getUID() : '(user not connected)'));
 				return;
 			}
 		}