[Backport 1.8.latest] add empty to context flags

[github-actions[bot]]

Backport 1475abb1cb51d4ed88d27393278588ed6c1584ee from #10315.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.31%. Comparing base (2ae5e32) to head (4ecfd61).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 1.8.latest #10319 +/- ## =========================================== Coverage 88.30% 88.31% =========================================== Files 181 181 Lines 22758 22758 =========================================== + Hits 20097 20099 +2 + Misses 2661 2659 -2 ``` | [Flag](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10319/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | Coverage Δ | | |---|---|---| | [integration](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10319/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | `85.60% <ø> (+0.04%)` | :arrow_up: | | [unit](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10319/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | `62.80% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs#carryforward-flags-in-the-pull-request-comment) to find out more.

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[MichelleArk]

@cla-bot check

[MichelleArk]

@cla-bot check

[cla-bot[bot]]

The cla-bot has been summoned, and re-checked this pull request!