Prevent suggest pipeline showing on invalid states

- should not show when in non open state or when
  source branch does not exist, since the next step
  is to go to web ide on the source branch and
  create a file.

app/serializers/merge_request_widget_entity.rb

@@ -95,7 +95,9 @@ class MergeRequestWidgetEntity < Grape::Entity
   end
 
   def can_add_ci_config_path?(merge_request)
-    merge_request.source_project&.uses_default_ci_config? &&
+    merge_request.open? &&
+      merge_request.source_branch_exists? &&
+      merge_request.source_project&.uses_default_ci_config? &&
       !merge_request.source_project.has_ci? &&
       merge_request.commits_count.positive? &&
       can?(current_user, :read_build, merge_request.source_project) &&

spec/serializers/merge_request_widget_entity_spec.rb

@@ -155,6 +155,36 @@ describe MergeRequestWidgetEntity do
             expect(subject[:merge_request_add_ci_config_path]).to be_nil
           end
         end
+
+        context 'when merge request is merged' do
+          before do
+            resource.mark_as_merged!
+          end
+
+          it 'returns a blank ci config path' do
+            expect(subject[:merge_request_add_ci_config_path]).to be_nil
+          end
+        end
+
+        context 'when merge request is closed' do
+          before do
+            resource.close!
+          end
+
+          it 'returns a blank ci config path' do
+            expect(subject[:merge_request_add_ci_config_path]).to be_nil
+          end
+        end
+
+        context 'when source branch does not exist' do
+          before do
+            resource.source_project.repository.rm_branch(user, resource.source_branch)
+          end
+
+          it 'returns a blank ci config path' do
+            expect(subject[:merge_request_add_ci_config_path]).to be_nil
+          end
+        end
       end
 
       context 'when user does not have permissions' do