"Never getting runtime errors" is as far fetched as it can be. Consider Xcode suggesting developers use force unwrap ("!"), that leads to many more crashes with unexperienced developers than the ObjC message to nil paradigm.

Subjectively, I have seen much more crashes in third-party software written in Swift than in ObjC (usually unwrapping or casting incorrectly), including in Apple's software. I cannot say if this is down to more inexperienced developers, less time allotted to experienced developers or a worse development model. I'd say a combination of the three.