While changing the icon, when 'Select Icon' and 'Texture2D' windows opened then after performing undo operation, these windows remain opened in the editor. Refer attached video.

Steps to repro:
1. Create a New Project.
2. Hierarchy > 3D object > Cube.
3. Cube > Inspector > Select Icon > Other.
4. Edit > Undo Selection Change.

Actual result:
'Select Icon' and 'Texture2D' windows remain open after performing undo operation.

Expected result:
'Select Icon' and 'Texture2D' windows should close as soon as undo operation is applied.

Reproducible in:
2021.2.0a1, 2021.1.0b2, 2020.2.2f1, 2020.1.17f1, 2019.4.18f1, 2018.4.30f1

Environment:
Occurring on Mac 10.15.