Cannot perform this action on a sealed instance

**元素定位**
* Cannot perform this action on a sealed instance

**描述问题bug**
执行poco执行元素操作报错
```
[09:46:43][DEBUG] find_best_result() ruTraceback (most recent call last):
File "C:\Users\chenxiaowu\Desktop\untitled.air\demo2.py", line 37, in
n time is 0.24 s. print(poco(text="关注").exists())
File "C:\Python37-32\lib\site-packages\poco\proxy.py", line 72, in wrapped
return func(proxy, *args, **kwargs)
File "C:\Python37-32\lib\site-packages\poco\proxy.py", line 774, in exists
return self.attr('visible')
File "C:\Python37-32\lib\site-packages\poco\proxy.py", line 39, in wrapped
return func(self, *args, **kwargs)
File "C:\Python37-32\lib\site-packages\poco\proxy.py", line 734, in attr
nodes = self._do_query(multiple=False)
File "C:\Python37-32\lib\site-packages\poco\proxy.py", line 872, in _do_query
self._nodes = self.poco.agent.hierarchy.select(self.query, multiple)
File "C:\Python37-32\lib\site-packages\poco\utils\retry.py", line 15, in wrapped
return func(*args, **kwargs)
File "C:\Python37-32\lib\site-packages\poco\utils\hrpc\hierarchy.py", line 33, in select
return self.selector.select(query, multiple)
File "C:\Python37-32\lib\site-packages\hrpc\object_proxy.py", line 92, in __call__
return self._client__.evaluate(self.__call_no_evaluate__(remote_obj_cache, *args))
File "C:\Python37-32\lib\site-packages\hrpc\client.py", line 81, in evaluate
raise RpcRemoteException(resp)
hrpc.exceptions.RpcRemoteException: java.lang.IllegalStateException: Cannot perform this action on a sealed instance.
```

**复现步骤**
```
poco = AndroidUiautomationPoco(use_airtest_input=True, screenshot_each_action=False)
print(poco(text="关注").exists())
```
实际上这个元素是存在的，并且执行任何操作都报这个错误

**预期效果**
正常识别

**相关截图**
(贴出遇到问题时的截图内容，如果有的话)

**python 版本:** `python3.7.3`

**poco 版本:** `1.0.79`

**设备:**
- 型号: [e.g. 华为 META 10]
- 系统: [e.g. Android 9]

**其他相关环境信息**
平台无关