The selected theme is not displayed in the `Theme` field

… of the `Appearance` tab of the `Preferences - CopyQ` window.

#### To Reproduce
1. Open the `Appearance` tab and select any theme.
2. Close the `Preferences - CopyQ` window by clicking OK.
3. Reopen the application settings window.
4. The `Theme` field appears empty.

#### Expected behavior
4. The `Theme` field displays the name of the previously selected theme.

#### Version, OS and Environment
- Application Version: 13.0.0
- OS: Microsoft Windows 10.0.26200.7019
- Mozilla Firefox 145.0 (64-bit)
- Installation method: `https://github.com/hluk/CopyQ/releases/download/v13.0.0/copyq-13.0.0.zip`

#### Additional context
The application is running as administrator.