Did you register it before they registered it? If yes then good go ahead.
If you registered it right now just to sell it to them, then also you can go ahead as they don't have any TM reg'd but approach a bit carefully.
Anyways i think you should be fine.
In my experience you are far better off selling a domain to someone when it is their idea, they'll be willing to pay more and be more willing to go through the process.
It's risky because unless you have the name registered before they made the TM then they can accuse you with acting in bad faith and you will lose the domain.