use actual head pipeline on merge request presenter

spec/models/merge_request_spec.rb

@@ -838,6 +838,14 @@ describe MergeRequest do
         expect(subject.head_pipeline).to be_nil
       end
+
+      context 'when the source project does not exist' do
+        it 'returns nil' do
+          allow(subject).to receive(:source_project).and_return(nil)
+
+          expect(subject.head_pipeline).to be_nil
+        end
+      end
     end
     describe '#actual_head_pipeline' do
@@ -855,6 +863,12 @@ describe MergeRequest do
         expect(subject.actual_head_pipeline).to eq(subject.head_pipeline)
         expect(subject.actual_head_pipeline).to eq(pipeline)
       end
+
+      it 'returns nil when source project does not exist' do
+        allow(subject).to receive(:source_project).and_return(nil)
+
+        expect(subject.actual_head_pipeline).to be_nil
+      end
     end
   end

spec/presenters/merge_request_presenter_spec.rb

@@ -31,7 +31,7 @@ describe MergeRequestPresenter do
       let(:pipeline) { build_stubbed(:ci_pipeline) }
       before do
-        allow(resource).to receive(:head_pipeline).and_return(pipeline)
+        allow(resource).to receive(:actual_head_pipeline).and_return(pipeline)
       end
       context 'success with warnings' do