[ty] hotfix panic in semantic tokens

[Gankra]

Fixes astral-sh/ty#1637

[astral-sh-bot]

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

[astral-sh-bot]

mypy_primer results

Changes were detected when running on open source projects

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
+ src/scikit_build_core/build/wheel.py:98:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 44 diagnostics
+ Found 45 diagnostics

dd-trace-py (https://github.com/DataDog/dd-trace-py)
- ddtrace/appsec/_handlers.py:404:13: error[invalid-argument-type] Argument to bound method `add_configurations` is incorrect: Expected `list[tuple[str, str, str]]`, found `list[Unknown | tuple[str, int, Unknown]] & list[tuple[str, str, str] | tuple[str, int, Unknown]]`
+ ddtrace/appsec/_handlers.py:404:13: error[invalid-argument-type] Argument to bound method `add_configurations` is incorrect: Expected `list[tuple[str, str, str]]`, found `list[tuple[str, str, str] | tuple[str, int, Unknown]] & list[Unknown | tuple[str, int, Unknown]]`

No memory usage changes detected ✅

[oconnor663]

astral-sh/ty@e1ebb31 pulls this into astral-sh/ty#1638.