[Bug] Squash-merging a stacked PR from the PR page ignores an emptied description and restores the original commit body

[KEY60228]

Thanks for the great work on stacked pull requests! I'd like to report one small bug on the merge UI:

Summary

This is about the github.com merge UI, not the CLI.

When I squash-merge a PR that belongs to a stack from its PR page, and I clear the "extended description" textarea before confirming, the resuElting squash commit still contains the body of the original branch commit. The same steps on a non-stacked PR in the same repository produce a squash commit with an empty body, as expected.

Replacing the description with any non-empty text is honored. Only the "empty" case is affected. It looks like the stack merge path treats an empty description as "not provided" and falls back to the default generated message, whereas the regular PR merge path respects the empty value.

Similar Issues and Discussions

Related but different: #493 / #285 / #311 (no edit form when merging a whole stack) and #209 (other message differences in the stack squash path).