A mission in Mantle caused an invalid vector access when checking whether to vaporize a ship whose ship type was -1. Turns out having "no type" is actually allowed, so I audited all `class_type` accesses throughout the code for potential -1 accesses. Most were properly checked but a few were not. A few others needed to be tweaked.
(I suspect this is something that would be on the Coverity list if it isn't already.)
Goober5000
4fbe3b7131