pull-requests: prevent from errors in generating a title in repositories which have

only 1 reference.

rhodecode/apps/repository/views/repo_pull_requests.py

@@ -608,7 +608,8 b' class RepoPullRequestsView(RepoAppView, '
         try:
             source_repo_data = PullRequestModel().generate_repo_data(
                 source_repo, commit_id=commit_id,
-                branch=branch_ref, bookmark=bookmark_ref, translator=self.request.translate)
+                branch=branch_ref, bookmark=bookmark_ref,
+                translator=self.request.translate)
         except CommitDoesNotExistError as e:
             log.exception(e)
             h.flash(_('Commit does not exist'), 'error')
@@ -627,7 +628,8 b' class RepoPullRequestsView(RepoAppView, '
             default_target_repo, translator=self.request.translate)
 
         selected_source_ref = source_repo_data['refs']['selected_ref']
-
+        title_source_ref = ''
+        if selected_source_ref:
         title_source_ref = selected_source_ref.split(':', 2)[1]
         c.default_title = PullRequestModel().generate_pullrequest_title(
             source=source_repo.repo_name,