Check if archive contains a directory named like appid

lib/private/installer.php

@@ -107,6 +107,9 @@ class OC_Installer{
 		}
 
 		$extractDir .= '/' . $info['id'];
+		if(!file_exists($extractDir)) {
+			throw new \Exception($l->t("Archive does not contain a directory named %s", $info['id']));
+		}
 		OC_Helper::copyr($extractDir, $basedir);
 
 		//remove temporary files