Fix new stock article failing

app/controllers/stockit_controller.rb

@@ -40,12 +40,11 @@ class StockitController < ApplicationController
   end
 
   def create
-    @stock_article = StockArticle.new(params[:stock_article])
-    if @stock_article.valid? && @stock_article.save
-      render :layout => false
-    else
-      render :action => 'new', :layout => false
-    end
+    @stock_article = StockArticle.new({quantity: 0}.merge(params[:stock_article]))
+    @stock_article.save!
+    render :layout => false
+  rescue ActiveRecord::RecordInvalid
+    render :action => 'new', :layout => false
   end
 
   def edit
@@ -56,11 +55,10 @@ class StockitController < ApplicationController
 
   def update
     @stock_article = StockArticle.find(params[:id])
-    if @stock_article.update_attributes(params[:stock_article])
-      render :layout => false
-    else
-      render :action => 'edit', :layout => false
-    end
+    @stock_article.update_attributes!(params[:stock_article])
+    render :layout => false
+  rescue ActiveRecord::RecordInvalid
+    render :action => 'edit', :layout => false
   end
 
   def show

app/models/stock_article.rb

@@ -5,6 +5,8 @@ class StockArticle < Article
 
   scope :available, -> { undeleted.where('quantity > 0') }
 
+  validates :quantity, presence: true, numericality: {greater_than_or_equal_to: 0}
+
   before_destroy :check_quantity
 
   # Update the quantity of items in stock
@@ -46,4 +48,3 @@ class StockArticle < Article
     true
   end
 end
-