Do not generate pipeline ref path if ref not present

app/serializers/pipeline_entity.rb

@@ -40,11 +40,13 @@ class PipelineEntity < Grape::Entity
     end
 
     expose :path do |pipeline|
+      if pipeline.ref
         namespace_project_tree_path(
           pipeline.project.namespace,
           pipeline.project,
           id: pipeline.ref)
       end
+    end
 
     expose :tag?, as: :tag
     expose :branch?, as: :branch

spec/serializers/pipeline_entity_spec.rb

@@ -134,5 +134,17 @@ describe PipelineEntity do
         expect(subject).not_to have_key(:yaml_errors)
       end
     end
+
+    context 'when pipeline ref is empty' do
+      let(:pipeline) { create(:ci_empty_pipeline) }
+
+      before do
+        allow(pipeline).to receive(:ref).and_return(nil)
+      end
+
+      it 'does not generate branch path' do
+        expect(subject[:ref][:path]).to be_nil
+      end
+    end
   end
 end