Nullable fields in AccessToken cause runtime crash

[PhuCG]

Problem

AccessToken getters declared non-nullable return types (String, num, List<String>), but values come from a raw Map<String, dynamic>. If any key is missing or null in the server response, Dart throws a runtime exception when casting null to a non-nullable type.

Crash stack trace:

Null check operator used on a null value
#0  AccessToken.tokenType (package:flutter_line_sdk/src/model/access_token.dart:99:32)

Root Cause

// Before — crashes if 'token_type' key is absent
String get tokenType => _data['token_type'];

_data['token_type'] returns dynamic. At runtime, Dart implicitly casts it to String. If the value is null, it throws immediately.

Fix

Changed affected getters to return nullable types:

Getter	Before	After
value	String	String?
expiresIn	num	num?
scopes	List<String>	List<String>?
tokenType	String	String?

// After — safe
String? get tokenType => _data['token_type'];
List<String>? get scopes => (_data['scope'] as String?)?.split(' ');

Changes

• lib/src/model/access_token.dart — updated getter return types
• test/flutter_line_sdk_test.dart — updated assertions to use null-aware operators