Icons get replaced by blue squares when opening Package Manager

Reproduction steps:
1. Create a new project
2. Open Window → Package Manager

Expected result: There are no blue squares in the Package Manager window
Actual result: Some of the icons are replaced with blue squares

Reproducible with: 2023.1.0a20, 2023.1.0a21
Not reproducible with: 2020.3.42f1, 2021.3.14f1, 2022.1.23f1, 2022.2.0f1, 2023.1.0a19

Reproducible on: macOS 13.0 (Intel)
Not reproducible on: Windows 10

Notes:

• If it doesn’t reproduce, close and reopen the project until it reproduces
• Some of the blue squares disappear after a second
• The blue squares disappear and the icons reappear when they get updated