No code query parameter in the redirect url throws exception

[DylanRJ]

Describe the bug
In testing our project authentication implementation using the AppAuth-iOS package, we have noticed that a redirect url without an authentication code parameter throws and NSException, crashing the app. This behaviour feels incorrect as we can't gracefully handle the situation in an error scenario.

To Reproduce
Steps to reproduce the behavior:

1. Go to demo implementation where the resource server has an option to return a redirect url with no code query parameter
2. Tap on option to return a redirect url with no code query parameter
3. See that app crashes

Expected behavior
We would expect that some kind of NSError would be returned to the authState callback which could then be handled.

Screenshots
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Environment

• Device: [ e.g. iPhone SE (2nd Generation ]
• OS: [ iOS 17.2 ]

Additional context
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