Update FileSizeHelper.cs

Try to make file size parsing work on systems with other locales

OpenDirectoryDownloader/Helpers/FileSizeHelper.cs

@@ -58,7 +58,7 @@ public static long ParseFileSize(string value, int kbValue = 1024, bool throwExc
                 }
 
                 // Get the numeric part.
-                double number = double.Parse(value.Substring(0, ext_start));
+                double number = double.Parse(value.Substring(0, ext_start), CultureInfo.InvariantCulture);
 
                 // Get the extension.
                 string suffix;