Vorta: Show error when trying to delete the last profile

[rugk]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Create a new profile at the top, the only/first one.
2. Click on the delete button.

What happens: Nothing.
What should happen: Either show an error or just delete the profile.

Environment (please complete the following information):

• OS: Fedora 33
• Vorta version: v0.7.5
• Installed from: Flathub

Additional context
nothing speical logged

[m3nu]

The last profile is never deleted, but there is no error message currently. We could probably add that.

[jzacsh]

What should happen: Either show an error or just delete the profile.

Same. Specifically I was expecting this to just get me back to the starting state of the first time I used the app (a clean slate).