fix: 修复购物车总价和价格格式化中的空值问题

修复了购物车总价计算中可能存在的空值问题，确保当 `item.price` 或 `item.quantity` 为空时不会导致计算错误。同时，修复了价格格式化函数中对空值的处理，避免显示异常。

@@ -93,7 +93,7 @@ export function provideCart(mode = CartMode.MULTIPLE) {
   // 计算购物车总价
   // 计算购物车总价
   function getTotalPrice() {
   function getTotalPrice() {
     return cartItems.value.reduce(
     return cartItems.value.reduce(
-      (total, item) => total + item.price * item.quantity,
+      (total, item) => total + ((item.price ?? 0) * (item.quantity ?? 0)),
       0
       0
     )
     )
   }
   }

@@ -45,7 +45,7 @@
               <div class="flex flex-1">
               <div class="flex flex-1">
                 <div class="w-12 h-12 rounded-lg overflow-hidden mr-3 flex-shrink-0">
                 <div class="w-12 h-12 rounded-lg overflow-hidden mr-3 flex-shrink-0">
                   <img
                   <img
-                    :src="item.imageUrl || '/assets/images/course-placeholder.jpg'"
+                    :src="item.cover || 'https://cdn.ipadbiz.cn/mlaj/images/default_block.png'"
                     :alt="item.title"
                     :alt="item.title"
                     class="w-full h-full object-cover"
                     class="w-full h-full object-cover"
                     @error="handleImageError"
                     @error="handleImageError"
@@ -54,7 +54,7 @@
                 <div class="flex-1">
                 <div class="flex-1">
                   <p class="font-medium text-sm line-clamp-1">{{ item.title }}</p>
                   <p class="font-medium text-sm line-clamp-1">{{ item.title }}</p>
                   <p class="text-xs text-gray-500">
                   <p class="text-xs text-gray-500">
-                    {{ item.type === 'course' ? '课程' : '活动' }} · {{ item.quantity }} 份
+                    {{ item.type === 'course' ? '课程' : '活动' }} · {{ item?.quantity }} 份
                   </p>
                   </p>
                 </div>
                 </div>
                 <button
                 <button
@@ -72,7 +72,7 @@
                 </button>
                 </button>
               </div>
               </div>
               <div class="ml-2 text-right">
               <div class="ml-2 text-right">
-                <p class="font-medium text-sm">{{ formatPrice(item.price * item.quantity) }}</p>
+                <p class="font-medium text-sm">{{ formatPrice(item?.price * item.quantity) }}</p>
                 <p class="text-xs text-gray-500">{{ formatPrice(item.price) }} / 份</p>
                 <p class="text-xs text-gray-500">{{ formatPrice(item.price) }} / 份</p>
               </div>
               </div>
             </div>
             </div>
@@ -302,7 +302,8 @@ const itemToDelete = ref(null)
 
 
 // Format price with Chinese Yuan symbol
 // Format price with Chinese Yuan symbol
 const formatPrice = (price) => {
 const formatPrice = (price) => {
-  return `¥${price.toFixed(2)}`
+  if (!price && price !== 0) return '¥0.00'
+  return `¥${Number(price).toFixed(2)}`
 }
 }
 
 
 // Handle image error
 // Handle image error