fix(handle): missing maker/taker fee arrays in order deserialization

[jrootcache]

Summary

Fixes a runtime edge case in order deserialization when fee arrays are missing from API responses.

Problem

deserializeOrder assumed maker_fees and taker_fees always exist and called .map() directly.
If either field is missing, SDK throws at runtime.

Fix

• Added null-safe fallbacks:
  • makerFees: (order.maker_fees ?? []).map(...)
  • takerFees: (order.taker_fees ?? []).map(...)

Tests

Added a unit test in test/orders/utils.spec.ts to verify missing fee arrays deserialize to empty arrays instead of throwing.

[ryanio]

LGTM. The ?? [] fallback for maker_fees and taker_fees is a solid defensive fix — the API response could omit these even though the type declares them as required. Test coverage is clean.