ok, I experimented with this a tiny bit, and it can be easily reproduced. here's what I did:
1) buy a new interceptor and a missile rack, but sell the missiles in your storage if any
2) equip the missile rack
3) send out the craft. no firing radius ring, well it shouldn't have one because it has no missiles.
4) buy some missiles and head back to base, missiles will be loaded automatically
now you should have an interceptor that can shoot missiles but lacks the radius ring.