Need to add basic 'revert-to-default' code for if the current fuel type has been changed/removed/etc.

Noticed this while loading up a LH2-enabled Delta-IV test vessel while I had the LH2 patch disabled; it errors out while loading the tank fuel type, causing the rest of the craft to not load.

Proper handling would revert the fuel-type to default if the 'current fuel type' is not found in the list of valid fuel types. This may require re-initializing the resources as well (if not in flight).

Fixed in dev; needs testing/validation