Last SVN rev 13399, when Torpedo's slot goes empty i'm not able to buy another one directly. It behaves as the slot was full, but there are 0 missiles remaining. The only way seems to be buying another kind of missiles and then replace them with a torpedo. This doesn't happen with other missiles like for es. dumbfire, by now i can't say if torpedos are the only ones. Issue present already in stable (0.5.1 r1) version.