firebase_auth: SAMLAuthProvider throws an error with loginWithSSOProvider

### Is there an existing issue for this?

- [x] I have searched the existing issues.

### Which plugins are affected?

Auth

### Which platforms are affected?

iOS

### Description

When `signInWithProvider` is called with `SAMLAuthProvider`, the login seems successful but it throws an error like below:

`loginWithSSOProvider error: type 'String' is not a subtype of type 'Map?'`

### Reproducing the issue

```
final provider = SAMLAuthProvider('saml.mycompany.com');

UserCredential userCredential = await FirebaseAuth.instance.signInWithProvider(provider);
```

### Firebase Core version

3.10.0

### Flutter Version

3.22.3

### Relevant Log Output

```shell
Error received from Flutter ["exceptionDescription": type 'String' is not a subtype of type 'Map?'#0 platformExceptionToFirebaseAuthException (package:firebase_auth_platform_interface/src/method_channel/utils/exception.dart:47:25), "stackTraceDescription": #0 platformExceptionToFirebaseAuthException (package:firebase_auth_platform_interface/src/method_channel/utils/exception.dart:47:25)
#1 convertPlatformException (package:firebase_auth_platform_interface/src/method_channel/utils/exception.dart:26:5)
#2 MethodChannelFirebaseAuth.signInWithProvider (package:firebase_auth_platform_interface/src/method_channel/method_channel_firebase_auth.dart:405:7)

#3 FirebaseAuth.signInWithProvider (package:firebase_auth/src/firebase_auth.dart:641:9)

]
```

### Flutter dependencies

Expand Flutter dependencies snippet

```
Dart SDK 3.4.4
Flutter SDK 3.22.3

dependencies:
...
- firebase_auth: ^5.4.0
- firebase_core: ^3.10.0
...
```

### Additional context and comments

Android also throws an error but it it different with iOS. The Android throws below error.

`loginWithSSOProvider error: [firebase_auth/unknown] https://myproject.firebaseapp.com/__/auth/handler?providerId= saml.mycompany.com `