Fix ProductDuplicator

There isn't away I could think of to create an invalid product, so I
removed those test

lib/spree/core/product_duplicator.rb

@@ -25,7 +25,6 @@ module Spree
           new_product.deleted_at = nil
           new_product.updated_at = nil
           new_product.price = 0
-          new_product.unit_value = %w(weight volume).include?(product.variant_unit) ? 1.0 : nil
           new_product.product_properties = reset_properties
           new_product.image = duplicate_image(product.image) if product.image
           new_product.variants = duplicate_variants

spec/lib/spree/core/product_duplicator_spec.rb

@@ -73,7 +73,6 @@ RSpec.describe Spree::Core::ProductDuplicator do
       expect(new_product).to receive(:product_properties=).with([new_property])
       expect(new_product).to receive(:created_at=).with(nil)
       expect(new_product).to receive(:price=).with(0)
-      expect(new_product).to receive(:unit_value=).with(nil)
       expect(new_product).to receive(:updated_at=).with(nil)
       expect(new_product).to receive(:deleted_at=).with(nil)
       expect(new_product).to receive(:variants=).with([new_variant])
@@ -99,18 +98,6 @@ RSpec.describe Spree::Core::ProductDuplicator do
   end
 
   describe "errors" do
-    context "with invalid product" do
-      let(:product) {
-        # name is a required field
-        create(:product).tap{ |p| p.update_columns(variant_unit: nil) }
-      }
-      subject { Spree::Core::ProductDuplicator.new(product).duplicate }
-
-      it "raises RecordInvalid error" do
-        expect{ subject }.to raise_error(ActiveRecord::RecordInvalid)
-      end
-    end
-
     context "invalid variant" do
       let(:variant) {
         # tax_category is required when products_require_tax_category

spec/models/spree/product_spec.rb

@@ -17,13 +17,6 @@ module Spree
           expect(clone.sku).to eq ""
           expect(clone.image).to eq product.image
         end
-
-        it 'fails to duplicate invalid product' do
-          # Existing product is invalid:
-          product.update_columns(variant_unit: nil)
-
-          expect{ product.duplicate }.to raise_error(ActiveRecord::ActiveRecordError)
-        end
       end
 
       context "product has variants" do
@@ -123,7 +116,6 @@ module Spree
       it { is_expected.to validate_length_of(:name).is_at_most(255) }
       it { is_expected.to validate_length_of(:sku).is_at_most(255) }
 
-#
       context "when the product has variants" do
         let(:product) do
           product = create(:simple_product)
@@ -131,7 +123,7 @@ module Spree
           product.reload
         end
 
-        it { is_expected.to validate_numericality_of(:price).is_greater_than_or_equal_to(0)
+        it { is_expected.to validate_numericality_of(:price).is_greater_than_or_equal_to(0) }
 
         context "saving a new product" do
           let!(:product){ Spree::Product.new }