fix(thinkOrder): 修复申请退款功能

- 添加退款原因的必填验证
- 优化退款金额的验证逻辑

src/views/think/thinkOrder/components/refund.vue

@@ -78,8 +78,12 @@
   };
 
   const save = async () => {
-    if (!form.refundAmount && props.data.price > 0)
+    if (!form.refundAmount && props.data.price > 0){
       return message.error('请输入退款金额');
+    }
+    if (form.refundReason == '' || !form.refundReason) {
+      return message.error('请输入退款原因');
+    }
     loading.value = true;
     await addThinkOrderRefundLog(form);
     loading.value = false;