Address AI feedback

Signed-off-by: Lukasz Gryglicki <lgryglicki@cncf.io>

Assisted by [OpenAI](https://platform.openai.com/)

Assisted by [GitHub Copilot](https://github.com/features/copilot)

Author: lukaszgryglicki

cla-backend-go/github/github_repository.go

@@ -1529,7 +1529,7 @@ func GetPRHeadSHA(ctx context.Context, gh *github.Client, owner, repo string, pr
 			"repo":          repo,
 			"pullRequestID": prNumber,
 		}
-		log.WithFields(f).WithError(err).Warnf("cannot get PR head SHA using PullRequests.Get: %+v, trying PullRequests.ListCommits", err)
+		log.WithFields(f).WithError(err).Warn("cannot get PR head SHA using PullRequests.Get, trying PullRequests.ListCommits")
 		opts := &github.ListOptions{PerPage: 1}
 		commits, resp, comErr := gh.PullRequests.ListCommits(ctx, owner, repo, prNumber, opts)
 		if comErr != nil {

cla-backend/cla/models/github_models.py

@@ -2648,8 +2648,12 @@ def update_pull_request(
         commit_obj = pull_request.head.repo.get_commit(last_commit_sha)
     except (GithubException, AttributeError, TypeError) as exc:
         cla.log.error(f"{fn} - PR {pull_request.number}: exception getting head.sha: {exc}")
-        commit_obj = pull_request.get_commits().reversed[0]
-        last_commit_sha = commit_obj.sha
+        try:
+            commit_obj = pull_request.get_commits().reversed[0]
+            last_commit_sha = commit_obj.sha
+        except Exception as exc2:
+            cla.log.error(f"{fn} - PR {pull_request.number}: exception getting last commit from PR commits: {exc2}")
+            last_commit_sha = None
     if not last_commit_sha:
         cla.log.error(f"{fn} - PR {pull_request.number}: missing head.sha; cannot create statuses")
         return