NestedSelect控件在amis3.5.2版本下显示不正常

#### 描述问题：

NestedSelect控件在amis3.5.2版本下显示不正常，箭头和选项框向上偏移

#### 截图或视频：


#### 如何复现（请务必完整填写下面内容）：

1. 你是如何使用 amis 的？
import sdk.js

2. amis 版本是什么？请先在最新 beta 版本测试问题是否存在
sdk3.5.2

3. 粘贴有问题的完整 `amis schema` 代码：
{
"type":"nested-select",
"label":"对比对象",
"name":"contrastObject",
"id":"u:0bf90cb0b687",
"onlyLeaf":true,
"source":{
"url":"productManage/findProductManageTree",
"method":"get"
},
"multiple":true,
"onlyChildren":true
}

4. 操作步骤
productManage/findProductManageTree接口返回值：
{
"msg": "查询成功",
"data": [
{
"children": [
{
"label": "123",
"value": "p-mm5rOOjU"
},
{
"label": "4444",
"value": "p-rWaNHDaU"
},
{
"label": "QQ",
"value": "p-sOpstfCr"
}
],
"label": "AA",
"uuid": "m-ydrvkzhm"
},
{
"children": [
{
"label": "123",
"value": "p-VVQUjVCU"
},
{
"label": "333",
"value": "p-eOt3C2Qm"
}
],
"label": "BB",
"uuid": "m-Tr4nXpSR"
}
],
"status": 0
}

Start by reproducing the issue with the supplied NestedSelect schema, SDK 3.5.2, and the described productManage/findProductManageTree response. Trace the NestedSelect rendering and positioning entry point to identify why the arrow and options panel shift upward; done means the control aligns correctly with the field while preserving the shown selection behavior.

Written by the indexing model from the issue text.