fix(confirm-order): 修复优惠券选择逻辑，确保在未选择优惠券时正确处理空数组

packages/app/src/pages/home/mall/confirm-order/index.vue

@@ -151,7 +151,7 @@ onLoad(async (query: { data: string }) => {
             </template>
             <template #append>
               <div class="flex items-center gap-1">
-                <template v-if="!selectedCoupons.length">
+                <template v-if="!selectedCoupons?.length">
                   <div
                     class="text-black/40 text-sm font-normal font-['PingFang SC'] leading-[10.18px]"
                   >