files_external SMB: throw InvalidArgument when user is not set

Signed-off-by: Anderson Luiz Alves <alacn1@gmail.com>

Author: alacn1

apps/files_external/lib/Lib/Backend/SMB.php

@@ -76,6 +76,9 @@ public function __construct(IL10N $l, Password $legacyAuth) {
 	public function manipulateStorageConfig(StorageConfig &$storage, IUser $user = null) {
 		$auth = $storage->getAuthMechanism();
 		if ($auth->getScheme() === AuthMechanism::SCHEME_PASSWORD) {
+			if(!is_string($storage->getBackendOption('user')) || !is_string($storage->getBackendOption('password')))
+				throw new \InvalidArgumentException('user or password is not set');
+
 			$smbAuth = new BasicAuth(
 				$storage->getBackendOption('user'),
 				$storage->getBackendOption('domain'),