fix(searchQueryBuilder): Add array guard to collapseTextTokens

[sentry]

This PR addresses JEST-274X, a TypeError: tokens.reduce is not a function occurring in collapseTextTokens within static/app/components/searchQueryBuilder/utils.tsx.

The root cause was identified as parseSearch (specifically after the 804a4be grammar refactor) returning a truthy non-array value for certain aggregate filter queries (e.g., p75(span.duration):>300ms test) when flattenParenGroups is enabled. The collapseTextTokens function previously only guarded against null values for tokens, but not against non-array types.

To fix this, a defensive check if (!Array.isArray(tokens)) { return null; } has been added to collapseTextTokens. This ensures that tokens is always an array before .reduce() is called, preventing the TypeError without altering the core parsing logic.

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Fixes JEST-274X

[github-actions]

📊 Type Coverage Diff

✅ No new type safety issues introduced. Coverage: 93.52%