Invalid configurations can be exported in the UI

Describe the bug

While an invalid configuration can't be submitted through the UI, it can be exported.

Trying to import that configuration in the UI isn't allowed, so it could be frustrating for a user who didn't realise that some values were invalid while exporting.

To Reproduce

Steps to reproduce the behavior:

1. Run Island
2. Add invalid configuration value somewhere
3. Try submitting and see warning box
4. Export and check the exported configuration for invalid value

Expected behavior

Don't allow exporting configuration if some values are invalid.

Screenshots

1. Added invalid IP to configuration

2. Export modal works normally, but a warning is shown on the configuration page

3. Warning box

4. Exported configuration