Fix some errors after cart refactor

front/src/lib/cart.ts

@@ -42,6 +42,13 @@ function createCartStore() {
                     )
                 });
         }
+
+        cart.update((cart: Record<string, CartItem>) => {
+            if (cart[uuid].amount <= 0) {
+                delete cart[uuid];
+            }
+            return cart;
+        })
     }
 
     function getEntries(): [string, CartItem][] {

front/src/pages/PageCart.svelte

@@ -12,15 +12,17 @@
 
     let items: [string, CartItem][];
     let totalPrice: number;
+    let totalItems: number;
 
     Cart.subscribe(() => {
         items = Cart.getEntries();
         totalPrice = Cart.getTotalPrice();
+        totalItems = Cart.getUniqueLength();
     });
 </script>
 
 
-{#if items.entries}
+{#if totalItems}
     <h1>Cart</h1>
 
     <button id="checkout-button">Checkout</button>