Update github_client.go

Add missing fix for github_client

server/events/vcs/github_client.go

@@ -611,7 +611,9 @@ func (g *GithubClient) MergePull(pull models.PullRequest, _ models.PullRequestOp
 	// Users can set their repo to disallow certain types of merging.
 	// We detect which types aren't allowed and use the type that is.
 	repo, resp, err := g.client.Repositories.Get(g.ctx, pull.BaseRepo.Owner, pull.BaseRepo.Name)
-	g.logger.Debug("GET /repos/%v/%v returned: %v", pull.BaseRepo.Owner, pull.BaseRepo.Name, resp.StatusCode)
+	if resp != nil {
+		g.logger.Debug("GET /repos/%v/%v returned: %v", pull.BaseRepo.Owner, pull.BaseRepo.Name, resp.StatusCode)
+	}
 	if err != nil {
 		return errors.Wrap(err, "fetching repo info")
 	}