do not set on_demand and on_hand if variant has errors

+ update specs

Co-Authored-By: Maikel <maikel@email.org.au>

app/services/sets/product_set.rb

@@ -114,6 +114,11 @@ module Sets
 
       variant = product.variants.create(variant_attributes)
 
+      if variant.errors.present?
+        product.errors.merge!(variant.errors)
+        return false
+      end
+
       begin
         variant.on_demand = on_demand if on_demand.present?
         variant.on_hand = on_hand.to_i if on_hand.present?

spec/services/sets/product_set_spec.rb

@@ -173,10 +173,8 @@ describe Sets::ProductSet do
                 end
 
                 it 'does not create variant and notifies bugsnag still raising the exception' do
-                  expect(Bugsnag).to receive(:notify)
                   number_of_variants = Spree::Variant.all.size
-                  expect { product_set.save }
-                    .to raise_error(StandardError)
+                  expect(product_set.save).to eq(false)
                   expect(Spree::Variant.all.size).to eq number_of_variants
                   expect(Spree::Variant.last.sku).not_to eq('321')
                 end