[1.0.3.3][Bug] You can upgrade ships to unbuildable ship designs.

There are a number of ship designs that are not supposed to be buildable by the player, however if you have got a compatible hull size you can upgrade to them.

The Drone interceptor can't be build in the shipyard, but a scout can be upgrade to it. The blueprint for the drone interceptor (DroneFighterBlueprint) has the CanBeBuilt tag set to false, which does prevent the ship from being build, but it does not prevent it from being upgrade to it.