fill `nil` criteria attributes with PointGroup::DEFAULT_CRITERIA

app/serializers/point_group_serializer.rb

@@ -4,4 +4,8 @@ class PointGroupSerializer < ApplicationSerializer
   def point_ids
     object.point_group_items.pluck(:point_id)
   end
+
+  def criteria
+    object.criteria || PointGroup::DEFAULT_CRITERIA
+  end
 end

spec/controllers/api/point_groups/show_spec.rb

@@ -17,4 +17,12 @@ describe Api::PointGroupsController do
     expect(response.status).to eq(200)
     expect(json.fetch(:name)).to eq pg.name
   end
+
+  it "fills `nil` criteria with PointGroup::DEFAULT_CRITERIA" do
+    pg = PointGroup.create!(name: "x", device: device, criteria: nil )
+    sign_in user
+    get :show, params: { id: pg.id }
+    expect(response.status).to eq(200)
+    expect(json.fetch(:criteria)).to eq PointGroup::DEFAULT_CRITERIA
+  end
 end