How to reproduce:
1. Create a new Project
2. Import ProBuilder and PolyBrush packages
3. In the Top-Menu click Tools -> ProBuilder -> ProBuilder Window
4. After the ProBuilder window is opened, observe the number of options available
5. In the Top-Menu click Tools -> Polybrush -> Polybrush Window
6. After the Polybrush window is opened, observe the ProBuilder window again

Expected results: After opening the Polybrush window, ProBuilder Edit modes are not disabled and the number of options in the ProBuilder window remains unaffected
Actual results: After the Polybrush window is opened, All ProBuilder Edit modes become disabled which forces the ProBuilder window to show only 3 options

Reproducible with package versions: 1.0.0, 1.0.2 (2019.4.32f1, 2020.3.22f1)
Not reproducible with package versions: 1.1.2(2019.4.32f1, 2020.3.22f1, 2021.1.28f1, 2021.2.1f1, 2022.1.0a13)

Workaround: After opening the Polybrush window, manually enable one of the ProBuilder Edit modes (Object/Face/Edge/Vertex) or interact with the Brush settings in the Polybrush window

Notes:
1. ProBuilder versions tested: 4.0.2, 4.5.2, 5.0.3, 5.0.4
2. Tested on Windows 10 and macOS 11.6.0