[Backend] Documents : correctif Vuejs getProductById()

backend/web/js/vuejs/document-form.js

         getProductById: function(idProduct) {
             var app = this;
 
-            for(var i = 0; i <= Object.keys(this.productsArray).length ; i++) {
+            for(var i = 0; i <= Object.keys(this.productsArray).length + 1 ; i++) {
                 if(app.productsArray[i] && app.productsArray[i].id == idProduct) {
                     return app.productsArray[i];
                 }