[ty] ty_ide: Hotfix for `expression_scope_id` panics (#18455)
## Summary
Implement a hotfix for the playground/LSP crashes related to missing
`expression_scope_id`s.
relates to: https://github.com/astral-sh/ty/issues/572
## Test Plan
* Regression tests from https://github.com/astral-sh/ruff/pull/18441
* Ran the playground locally to check if panics occur / completions
still work.
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Co-authored-by: Andrew Gallant <andrew@astral.sh>
