fix: emit NULL literal for nil values in SelectInlineResults

[TheRillJon]

• BigQuery's Go client rejects nil in bigquery.QueryParameter.Value
• When a two-phase comparison aggregation returns NULL dimension values (e.g. acquisition_channel is NULL in some rows), getArgExpr was emitting a ? placeholder with a nil arg
• Now emits a SQL NULL literal instead, and skips appending nil to the positional args slice

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

---

Developed in collaboration with Claude Code

[begelundmuller]

LGTM

[pjain1]

Just saw this PR and this is not needed for CH as its driver handles null values correctly, same for duckdb.

[pjain1]

I did a brief test on CLI and seems to work with this also.

[k-anshul]

Hey @pjain1

So just below this line there is this check :

if typ == runtimev1.Type_CODE_DATE {
  t, ok := val.(time.Time)
  if !ok {
	  return "", nil, fmt.Errorf("could not cast value %v to time.Time for date type", val)
  }
  return "toDate(?)", t.Format(time.DateOnly), nil
}

For nil values it will return error: could not cast value nil....
Is there any issue with adding this check ? That will make the below condition safer.

[pjain1]

OK got it, no issues with the check.