A new instance of "Export Noice to Texture" window is created every time even though another instance is already open in Noice Settings, refer to the attached video.

Steps to repro:
1. Create a new project
2. Windows > Package Manager > TerrainTools > Install
3. Project > right-click > Create > Noice Settings
4. Project > Noice Settings > Inspector > Export > Select multiple times

Actual Result:
A new instance of the "Export Noice to Texture" window created every time.

Expected Result:
Should update the already opened "Export Noice to Texture" window instead of creating a new instance of the window

Reproducible in:
2020.2.0a20, 2020.1.2f1, 2019.3.14f1 with Package Version 3.0.1, 3.0.0 , 2.0.2,1.1.2-preview,
2019.2.0a1 with Package Version 1.1.2-preview

Environment:
Windows 10 and macOS 10.14