ERC20Custodian : Freeze function bug with partial frozen balance

[ruhulamin1398]

Problem

The freeze function in ERC20Custodian currently only allows freezing tokens up to the user’s available (unfrozen) balance. This causes a bug where attempts to freeze the full balance fail if part of it is already frozen.

Expected Behavior

Custodians should be able to freeze tokens up to the user’s total token balance, regardless of how much is currently frozen.

Impact

This limitation makes it difficult to adjust frozen amounts dynamically and complicates custodian token management.

---

This issue is addressed in PR #189 which updates the freeze function to validate against the total balance instead of available balance.

[ruhulamin1398]

@ernestognw