How to deal with the Ecommerce web site Categories which does not contain or available product?

I'm not sure if that's a code-related question or a more general business question. In either case, you'd want to let the website visitor know that there are no available products for that category, and that they should check back again for product availability.

Are you talking about Out of stock products, that re not available for some time. Yes, you can do it by using preorder feature. I have used this preorder feature in PrestaShop and that helped me a lot to know about the prodcut demand.

well usually in this situation everyone used an upsell feature or provide a discount on that product in future date just to retain the prospect. this upsell and discount feature are present in lots of CRM so....i suggest you should use those.
I hope i helped!