Swift 6 crash

Describe the bug
I'm seeing an unexpected crash inside AppAuthCore when the module that calls into AppAuth is in Swift 6 mode.
Setting

swiftSettings: [
  .swiftLanguageMode(.v5),
]

makes the crash go away.

To Reproduce
Steps to reproduce the behavior:

let request = OIDAuthorizationRequest(
  configuration: config,
  clientId:clientId,
  scopes: nil,
  redirectURL: URL(string: redirectUri)!,
  responseType: OIDResponseTypeCode,
  additionalParameters: nil
)
OIDAuthState.authState(
  byPresenting: request,
  presenting: NSApp.keyWindow ?? NSWindow()
) { authState, error in ... }

then dismiss Safari and get an EXC_BREAKPOINT crash on the line callback(nil, authorizationError); in OIDAuthState.m

Expected behavior
The Swift 5 behaviour: The same library line is still hit, but no crash occurs

Environment

• Device: [ MacBook Pro ]
• OS: [ macOS 15.0 ]
• Browser: [ Safari ]

Reproduce the authorization flow in Swift 6 mode on macOS 15, then inspect the callback at callback(nil, authorizationError) in OIDAuthState.m. Compare the behavior with Swift 5 mode and determine what change prevents the EXC_BREAKPOINT while preserving the existing authorization error callback behavior.