GH-35943: [Dev] Ensure link issue works when PR body is empty

[raulcd]

Rationale for this change

Fix a bug when PR body is empty and Dev workflow fails.

What changes are included in this PR?

Ensure the link issue comment works in case of description being empty.

Are these changes tested?

I have tested it on my fork here: raulcd#81

Are there any user-facing changes?

No

• Closes: [Dev] Dev PR workflow fails to add link to GH issue if the body of PR is empty #35943

[github-actions]

⚠️ GitHub issue #35943 has been automatically assigned in GitHub to PR creator.

[kou]

+1

[raulcd]

👍

[conbench-apache-arrow]

Conbench analyzed the 6 benchmark runs on commit 0df414e1.

There were 3 benchmark results indicating a performance regression:

• Commit Run on ursa-thinkcentre-m75q at 2023-07-07 13:06:06Z
  • params=<Subtract, UInt64Type>/size:524288/inverse_null_proportion:100, source=cpp-micro, suite=arrow-compute-scalar-arithmetic-benchmark
  • params=<Subtract, UInt64Type>/size:524288/inverse_null_proportion:0, source=cpp-micro, suite=arrow-compute-scalar-arithmetic-benchmark
• and 1 more (see the report linked below)

The full Conbench report has more details.