fix: add None guard for params in get_balance_allowance and update_balance_allowance

[Sush78]

Overview

Fix AttributeError crash in get_balance_allowance and update_balance_allowance when called without params argument.

Description

Both methods declare params: BalanceAllowanceParams = None as optional but immediately access params.signature_type without a None check. This causes an opaque AttributeError: 'NoneType' object has no attribute 'signature_type' when called without params.

This adds a guard at the top of each method that raises a clear ValueError("params is required for ...") before accessing any attributes.

No change to method signatures or behaviour for callers who pass params correctly.

This bug was also flagged during code review of #224.

Testing instructions

Run the new test file: pytest tests/test_balance_allowance.py

Types of changes

• Refactor/enhancement
• Bug fix/behavior correction
• New feature
• Breaking change
• Other, additional

Notes

Fixes #306

Status

• Prefix PR title with [WIP] if necessary (changes not yet made).
• Add tests to cover changes as needed.
• Update documentation/changelog as needed.
• Verify all tests run correctly in CI and pass.
• Ready for review/merge.

---

Note

Low Risk
Low risk: adds early input validation and tests, without changing request construction for valid callers.

Overview
Fixes a crash in ClobClient.get_balance_allowance and ClobClient.update_balance_allowance by explicitly rejecting missing params with a clear ValueError before accessing params.signature_type.

Adds unit tests asserting both methods raise when called without parameters.

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