When I click the build ship button from the main screen, a pop-up window appears to choose a model. This list includes vessel designs that I've saved from previous games, but don't yet have the technology to purchase.

The display shows a 'purchasable' ship, the details box shows that all it's stats have been zeroed out. If I buy one, a ship with 0 hit points appears.

This could be fixed by having the build-ship box not display ships that I don't have the tech to build. For the shipyards, ships that are short one or more techs could be greyed out.