a slight rework of 955 to keep a seperation of concerns

[McKnight-42]

resolves #
docs dbt-labs/docs.getdbt.com/#

Problem

we implemented a change in #955 to fix query_header in doing so moved self.query_header into the same conditional logic as self.profile and used a walrus operator to assign and check which while clean does make parse code quickly slightly harder.

Solution

to functionalize the small snippet and create a small change by making it to two nested if statements and moving the empty set of variable to top of function.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-bigquery contributing guide.

[VersusFacit]

Big fan of this assuming the tests are all happy and you've tested the semantics :) The function gets us bonus documentation as to what/why is happening!

Thanks for being detail oriented!