add verification for AugmentationCost

[gmriggs]

AugmentationDevice.VerifyRequirements() was using AugmentationCost ?? 0, and the rest of the functions were using AugmentationCost directly

This had the effect of letting an AugmentationDevice w/ missing/bad data go through, resulting in undefined behavior afterwards, such as setting AvailableExperience to null

Adding check to AugmentationDevice.VerifyRequirements() to ensure AugmentationCost is not null