Why does sp_whoisactive show locks on databases, but not tables?
It means someone has a connection open in that database. You can reproduce it by:

USE NOG_APP;
GO
BEGIN TRAN;
GO


And then checking sessions from another window:

sp_WhoIsActive @get_locks = 1;


If you think that's your biggest problem, though, it's probably time to check in with users and ask them about their biggest database complaints. I think you're probably barking up the wrong tree. I can only wish my biggest problem would be open sleeping transactions with nothing locked....