bug(linux): The "Back" button does not turn to enable state when result is shown.

### Describe the bug

The "Back" button does not revert to the enabled state once the results are displayed.

### Reproduce the bug

I tested this issue with "Keyman 18.0.124-alpha (18.0.124-1~sil1~focal) build on the Ubuntu Focal environment. Here is my observation.
Steps to reproduce:
1. Installed the "Keyman 18.0.124-alpha" and gave all permissions to the application.
2. Installed the "Khmer Angkor" keyboard on the "Keyman Configuration" dialog.
3. Open the "keyman configuration" dialog.
4. Click the "Download Keyboard" button to open the "Download keyman keyboards" dialog.
5. Enter a keyboard name into the search box.
6. Click the "search" button.
Actual results: The search results appear, but the "Back" button does not revert to the enabled state once the results are displayed.
Please refer to the attached screenshot

### Expected behavior

_No response_

### Related issues

_No response_

### Keyman apps

- [ ] Keyman for Android
- [ ] Keyman for iPhone and iPad
- [X] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [ ] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

Keyman 18.0.124-alpha

### Operating system

Ubuntu OS Focal

### Device

_No response_

### Target application

_No response_

### Browser

_No response_

### Keyboard name

_No response_

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_