What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?

What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?

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How to provide a localized description with an Error type in Swift?

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Error-Handling in Swift-Language

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try, try! & try? what’s the difference, and when to use each?

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What are the differences between throws and rethrows in Swift?

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Converting ErrorType to NSError loses associated objects

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What's Dead & Exploded in Swift's exception stack?

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Error Handling in Swift 3

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Why does Realm use try! in Swift?

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Swift Error Handling For Methods That Do Not Throw [duplicate]

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Handling errors in Swift

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How should I use NSSetUncaughtExceptionHandler in Swift

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How do I get the error message in Swift 2.0?

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What to do with Swift's "try?" that cause "Result of try? is unused"? [duplicate]

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How to find the kind of errors a method may throw and catch them in Swift [duplicate]

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