don't throw errors if certificate folder doesn't exist

apps/files_external/lib/config.php

@@ -109,10 +109,10 @@ class OC_Mount_Config {
 		return $personal;
 	}
 
-	/**
-	 * Add directory for mount point to the filesystem
-	 * @param OC_Fileview instance $view
-	 * @param string path to mount point
+	/**
+	 * Add directory for mount point to the filesystem
+	 * @param OC_Fileview instance $view
+	 * @param string path to mount point
 	 */
 	private static function addMountPointDirectory($view, $path) {
 		$dir = '';
@@ -288,6 +288,9 @@ class OC_Mount_Config {
 		if (!is_dir($path)) mkdir($path);
 		$result = array();
 		$handle = opendir($path);
+		if (!$handle) {
+			return array();
+		}
 		while (false !== ($file = readdir($handle))) {
 			if($file != '.' && $file != '..') $result[] = $file;
 		}