[Android] `PlatformException`: `Failed to handle addContacts: Group has no account: <groupId>` when `getDefault()` returns null

[Eunno-An]

Description

On certain Android devices (e.g., LG devices running LG UX/Android 9/10), calling FlutterContacts.groups.addContacts() throws a PlatformException with the message:
Failed to handle addContacts: Group has no account: <groupId>.

This occurs because FlutterContacts.accounts.getDefault() returns null on these devices. Consequently, passing account: null to FlutterContacts.groups.create() creates a group in the Android Contacts database without ACCOUNT_NAME and ACCOUNT_TYPE. When addContacts() is subsequently called on that group ID, the native Android plugin implementation fails because the group is not associated with any account.

Environment

• Device: LG Q9 (LG UX, Android 9 / 10)
• Plugin: flutter_contacts
• Platform: Android

Steps to Reproduce

1. Execute final account = await FlutterContacts.accounts.getDefault(); (Returns null on affected devices).
2. Create a group:
   final group = await FlutterContacts.groups.create('Test Group', account: account);
3. Create a contact
   final contactId = await FlutterContacts.create(Contact(name: Name(first: 'John')));
4. Attempt to add the contact to the created group
   await FlutterContacts.groups.addContacts(
   groupId: group.id,
   contactIds: [contactId],
   );

Actual Behavior

I/flutter: PlatformException(flutter_contacts_error, Failed to handle addContacts: Group has no account: 17, null, null)

Expected Behavior

Either FlutterContacts.accounts.getDefault() should fallback to the first available account from FlutterContacts.accounts.getAccounts() if default account resolution returns null.
Or FlutterContacts.groups.create() / addContacts() should handle account: null gracefully without failing when adding contacts to groups on Android.

Proposed Solution / Workaround

Developers currently need to manually fallback to existing accounts when getDefault() returns null:

final accounts = await FlutterContacts.accounts.getAccounts();
Account? account;
if (accounts.isNotEmpty) {
account = accounts.firstWhere(
(a) => a.type == 'com.google',
orElse: () => accounts.first,
);
} else {
account = await FlutterContacts.accounts.getDefault();
}