[BUG] AvatarGroup修改zIndex属性报错: Uncaught (in promise): Cannot read properties of undefined (reading 'style')

### NutUI 包名

@nutui/nutui-taro

### NutUI 版本号

4.2.6

### 平台

weapp

### 重现链接

https://nutui.jd.com/playground/#eyJBcHAudnVlIjoiPHNjcmlwdCBzZXR1cCBsYW5nPVwidHNcIj5cbmltcG9ydCB7IERvbmdkb25nIH0gZnJvbSAnQG51dHVpL2ljb25zLXZ1ZSdcbjwvc2NyaXB0PlxuPHRlbXBsYXRlPlxuICA8bnV0LWF2YXRhci1ncm91cCBtYXgtY291bnQ9XCIzXCIgIG1heC1jb250ZW50PVwiLi4uXCIgc3Bhbj1cIi0xNlwiIHpJbmRleD1cInJpZ2h0XCI+XG4gICAgICA8bnV0LWF2YXRhcj5cbiAgICAgICAgICA8RG9uZ2RvbmcgLz5cbiAgICAgIDwvbnV0LWF2YXRhcj5cbiAgPC9udXQtYXZhdGFyLWdyb3VwPlxuPC90ZW1wbGF0ZT4ifQ==

### 重现步骤

```





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### 期望的结果是什么？

1.`z-index`属性改为`right`时, 当头像数量小于max-count时不显示max-content的内容

2.控制台不报错: `Uncaught (in promise): Cannot read properties of undefined (reading 'style')`

### 实际的结果是什么？

1.方向改成right后, 即使头像数量小于`max-count`也会显示`max-content`的内容
2.控制台报错`Uncaught (in promise): Cannot read properties of undefined (reading 'style')`

### 环境信息

_No response_

### 其他补充信息

_No response_