Seriously, if you use your common sense then you'll be fine. Yes, there is a chance that if you're walking through St Anns at 2am then you might get mugged, but firstly, isn't that the same for anywhere? And secondly, what would you be doing walking through St Anns at 2am? It's only the people who do silly things like that who get in any trouble.
As a Trent uni student, you'll pretty much be in the city centre for everything you do, you have zero need to wander into the 'rough' areas and I doubt you will, so you'll be fine.