Fix wrong filename

MD_STD.php

@@ -44,7 +44,7 @@ public static function file_get_contents(string $filename):string {
     public static function scandir(string $filepath):array {
 
         if (!is_dir($filepath) || ($output = scandir($filepath)) === false) {
-            throw new MDFileDoesNotExist("There is no file {$filename}");
+            throw new MDFileDoesNotExist("There is no file {$filepath}");
         }
 
         return array_values(array_diff($output, ['.', '..']));