Uninstalling a plugin that is in the saved configuration causes the configuration to fail to load

## Describe the bug
If I configure the Monkey to use a plugin, and then uninstall the plugin, the configuration page does not load fully.

## To Reproduce
Steps to reproduce the behavior:
1. Install a plugin
2. Configure the Monkey to use the installed plugin, and save the configuration
3. Uninstall the plugin
4. Go back to the configuration page. The only thing that is shown are the buttons (they aren't clickable)

## Expected behavior
I might expect the saved configuration to be updated to remove the plugin. It would be nice to have a dialog tell me that the plugin is in use when I try to uninstall it.

## Screenshots
Coming soon

## Machine version (please complete the following information):
- OS: Windows or Linux