Dunno if it's a common problem with the 9-3 or not, but I had exactly the same problem develop with mine.
The good news is it's very easy and cheap to fix.
When you open the glove box door you'll see two rubber bump stops either side of the compartment. What you need to do is carefully pull them out and pop down to B & Q to get some thin rubber washers pack them out.
When done, you'll see that as the door shuts it'll make contact with the now raised bumps and stop the rattle