iOS 10 Xcode 8 Swift 3 Error tutorials: EXC_BAD_INSTRUCTION error

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In this video we learned how to resolve the EXC_BAD_INSTRUCTION error, in which the value you are displaying is nil.

code: https://drive.google.com/open?id=0B6XbJ6zTtWCcZFljZWlBWDFNbEU .