Handle legacy jobs without name

Older pipelines can contain jobs without a name, in which case
'nameless' is used right now, so we can properly still handle other
actions on these jobs.

Fixes gitlab-org/gitlab-ce#33403

app/models/commit_status.rb

@@ -112,7 +112,7 @@ class CommitStatus < ActiveRecord::Base
   end
 
   def group_name
-    name.gsub(/\d+[\s:\/\\]+\d+\s*/, '').strip
+    name.to_s.gsub(/\d+[\s:\/\\]+\d+\s*/, '').strip
   end
 
   def failed_but_allowed?
@@ -156,7 +156,7 @@ class CommitStatus < ActiveRecord::Base
   end
 
   def sortable_name
-    name.split(/(\d+)/).map do |v|
+    name.to_s.split(/(\d+)/).map do |v|
       v =~ /\d+/ ? v.to_i : v
     end
   end

changelogs/unreleased/zj-commit-status-sortable-name.yml

+---
+title: Handle nameless legacy jobs
+merge_request:
+author:

spec/models/ci/legacy_stage_spec.rb

@@ -55,6 +55,17 @@ describe Ci::LegacyStage, :models do
       expect(stage.groups.map(&:name))
         .to eq %w[aaaaa rspec spinach]
     end
+
+    context 'when a name is nil on legacy pipelines' do
+      before do
+        pipeline.builds.first.update_attribute(:name, nil)
+      end
+
+      it 'returns an array of three groups' do
+        expect(stage.groups.map(&:name))
+          .to eq ['', 'aaaaa', 'rspec', 'spinach']
+      end
+    end
   end
 
   describe '#statuses_count' do