fix(ObjectStore): Fix regression when hostname is empty

Fixes #45637

The support for s3-accelerate added in #44496 introduced a regression in AWS S3 environments when `hostname` is blank (which is a valid configuration w/ AWS since the hostname gets auto-generated).

Signed-off-by: Josh <josh.t.richards@gmail.com>

lib/private/Files/ObjectStore/S3ConnectionTrait.php

@@ -44,7 +44,7 @@ protected function parseParams($params) {
 		$this->copySizeLimit = $params['copySizeLimit'] ?? 5242880000;
 		$this->useMultipartCopy = (bool)($params['useMultipartCopy'] ?? true);
 		$params['region'] = empty($params['region']) ? 'eu-west-1' : $params['region'];
-		$params['s3-accelerate'] = $params['hostname'] == 's3-accelerate.amazonaws.com' || $params['hostname'] == 's3-accelerate.dualstack.amazonaws.com';
+		$params['s3-accelerate'] = isset($params['hostname']) && ($params['hostname'] === 's3-accelerate.amazonaws.com' || $params['hostname'] === 's3-accelerate.dualstack.amazonaws.com');
 		$params['hostname'] = empty($params['hostname']) ? 's3.' . $params['region'] . '.amazonaws.com' : $params['hostname'];
 		if (!isset($params['port']) || $params['port'] === '') {
 			$params['port'] = (isset($params['use_ssl']) && $params['use_ssl'] === false) ? 80 : 443;