ToggleGroupControl: Missing border when initial value is undefined

[mirka]

Description

When the initial value of a ToggleGroupControl is undefined, there is a missing border after the first item.

Step-by-step reproduction instructions

  <ToggleGroupControl value={undefined} >
    <ToggleGroupControlOption
      key="foo"
      label="foo"
      value="foo"
    />
    <ToggleGroupControlOption
      key="bar"
      label="bar"
      value="bar"
    />
  </ToggleGroupControl>

Screenshots, screen recording, code snippet

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[amustaque97]

I will be working on this issue. Will link a PR soon 😄

[ntsekouras]

Fixed by: #35409