- If custom property value is null insert empty string (This will avoid crashing the AddProperty. Another way would be to throw an application exception, but it's much more intuitive to set an empty string instead.)
- Check if stream can seek (This will allow devs to save the document directly on a System.Web.HttpResponseStream without the need to create yet another memory stream.)
- Fix duplicate custom properties (Check if property exists ignoring case as it would produce a corrupted docx otherwise.)