How to reproduce:
1. Open the user’s attached “test_project.zip” project
2. Select any GameObject in the Hierarchy and lock the Inspector window
3. Go to Menu > Tools > ProBuilder > Editors > New PolyShape
4. Observe the result

Expected result: No errors, and the window doesn’t open again after pressing the cancel button
Actual result: Multiple errors appear, and the window keeps reopening after pressing the cancel button

Reproducible with: 6.0.1-pre.1 (2023.3.0a17, 2023.3.0b4)
Not reproducible with: 5.2.2 (2021.3.34f1, 2022.3.18f1, 2023.2.7f1, 2023.3.0a17)

Reproduced on: macOS 13.6.3 (Intel)
Not reproducible on: No other environment tested

Note: when using older ProBuilder package versions, it's needed to add a new shape from the ProBuilder window and select it