guard against variants that use items but have scales

app/services/weights_and_measures.rb

@@ -14,7 +14,7 @@ class WeightsAndMeasures
   end
 
   def system
-    scales = scales_for_variant_unit
+    return "custom" unless scales = scales_for_variant_unit
     return "custom" unless product_scale = @variant.product.variant_unit_scale
 
     scales[product_scale.to_f]['system']

spec/services/weights_and_measures_spec.rb

@@ -37,11 +37,17 @@ describe WeightsAndMeasures do
     end
 
     context "items" do
-      it "when scale is for items" do
+      it "when variant unit is items" do
         allow(product).to receive(:variant_unit) { "items" }
         allow(product).to receive(:variant_unit_scale) { nil }
         expect(subject.system).to eq("custom")
       end
+
+      it "when variant unit is items, even if the scale is present" do
+        allow(product).to receive(:variant_unit) { "items" }
+        allow(product).to receive(:variant_unit_scale) { 1.0 }
+        expect(subject.system).to eq("custom")
+      end
     end
   end