[FIX] website_sale: prevent search bar bug

Issue

	When pressing UP or DOWN arrow in search bar with empty text a traceback
	occurs.

Step to Reproduce

	- Install website_sale "eCommerce" application
	- Go to Website
	- Go to Shop
	- Click in Search Bar
	- Press Up or Down Key

Cause

	When no text is entered in the search bar, the $menu is undefined
	so trying to access children causes the error

Solution

	Test that $menu is defined prior to try accessing its children

task id-2252923

closes odoo/odoo#52161

Forward-port-of: #51920
X-original-commit: 30785e68852fa3cd18be11fcbaad4e886d01301c
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

addons/website_sale/static/src/snippets/s_products_searchbar/000.js

@@ -123,12 +123,12 @@ publicWidget.registry.productsSearchBar = publicWidget.Widget.extend({
                 this._render();
                 break;
             case $.ui.keyCode.UP:
-                ev.preventDefault();
-                this.$menu.children().last().focus();
-                break;
             case $.ui.keyCode.DOWN:
                 ev.preventDefault();
-                this.$menu.children().first().focus();
+                if (this.$menu) {
+                    let $element = ev.which === $.ui.keyCode.UP ? this.$menu.children().last() : this.$menu.children().first();
+                    $element.focus();
+                }
                 break;
         }
     },