Correct the logic for detecting if a motor has an invalid
FlightConfigurationId and throw an IllegalStateException only in the
case that it has an error.
Additionally, fix the lookup for the stageMass. The wrong value was
passed to the MassCalculator.getCGAnalysis(..) which resulted in
a NullPointerException.
Fixes#531
Signed-off-by: Billy Olsen <billy.olsen@gmail.com>