材质属性获取不到报错，有些材质确实没有这个属性

(请尽量按照下面提示内容填写，有助于我们快速定位和解决问题，感谢配合。否则直接关闭。)

**(重要！问题分类)**
* 图像识别相关问题 -> https://github.com/AirtestProject/Airtest/issues
* 测试开发环境AirtestIDE使用问题 -> https://github.com/AirtestProject/AirtestIDE/issues
* 控件识别、树状结构、poco库报错 -> 此仓库

**描述问题bug**
unity游戏，获取属性的时候报错

```
Material doesn't have a color property '_Color'
UnityEngine.Material:get_color()
Poco.UnityNode:GetImageSourceTexture() (at Assets/Scripts/Unity3D/ugui/UnityNode.cs:450)
Poco.UnityNode:GetPayload() (at Assets/Scripts/Unity3D/ugui/UnityNode.cs:141)
Poco.UnityNode:enumerateAttrs() (at Assets/Scripts/Unity3D/ugui/UnityNode.cs:126)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:32)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchyImpl(AbstractNode, Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:43)
Poco.AbstractDumper:dumpHierarchy(Boolean) (at Assets/Scripts/Unity3D/sdk/AbstractDumper.cs:22)
PocoManager:Dump(List`1) (at Assets/Scripts/Unity3D/PocoManager.cs:125)
RPCParser:HandleMessage(String) (at Assets/Scripts/Unity3D/PocoManager.cs:260)
<>c__DisplayClass22_0:b__0(String) (at Assets/Scripts/Unity3D/PocoManager.cs:195)
System.Collections.Generic.List`1:ForEach(Action`1)
PocoManager:Update() (at Assets/Scripts/Unity3D/PocoManager.cs:190)

```
**python 版本:** `python3.6`

**Airtest:** `1.2.6`
**poco版本:** `1.0.81`

**设备:**
- 型号: unity编辑器