[Regression] External nodes not included in catalog during docs generation

[MichelleArk]

Is this a regression in a recent version of dbt-core?

• I believe this is a regression in dbt-core functionality
• I have searched the existing issues, and I could not find an existing issue for this regression

Current Behavior

External nodes should be included in the catalog as a result of dbt docs generate. Currently, projects with external nodes are not included in the resulting catalog.json

Expected/Previous Behavior

catalog.json includes catalog entry for external node when project contains external node.

Steps To Reproduce

test passes 1.6.latest: #9457
same test fails on main (and 1.7.latest, confirmed locally): #9456

Relevant log output

No response

Environment

- OS:
- Python:
- dbt (working version): 1.6.9
- dbt (regression version): 1.7.5, 1.8.0a2

Which database adapter are you using with dbt?

No response

Additional Context

No response