Fixed deletion of quantity formula

app/controllers/quantities_controller.rb

@@ -113,9 +113,11 @@ class QuantitiesController < ApplicationController
       :description,
       formula_attributes:
       [
+        :id,
         :code,
         :zero_nil,
-        :unit_id
+        :unit_id,
+        :_destroy
       ]
     )
   end

app/models/quantity.rb

@@ -14,7 +14,10 @@ class Quantity < ActiveRecord::Base
 
   has_one :formula, inverse_of: :quantity, dependent: :destroy, validate: true
   accepts_nested_attributes_for :formula, allow_destroy: true,
-    reject_if: proc { |attrs| attrs['code'].blank? }
+    reject_if: proc { |attrs| attrs['id'].blank? && attrs['code'].blank? }
+  before_validation do
+    formula.mark_for_destruction if formula.present? && formula.code.blank?
+  end
 
   validates :name, presence: true
   # Quantity :name uniqueness relaxed to formulas unambiguity