Dont use $info as array when its not an array

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/Installer.php

@@ -107,7 +107,7 @@ class Installer {
 		if(!is_array($info)) {
 			throw new \Exception(
 				$l->t('App "%s" cannot be installed because appinfo file cannot be read.',
-					[$info['name']]
+					[$appId]
 				)
 			);
 		}