Fixed QuickInput behavior on Enter

[federicobozzini]

What it does

It fixes #11979. When clicking enter the first element of a QuickInput is picked by default.

How to test

1. Open a git-versioned project with Theia
2. Click on the branch name in the status bar (the QuickInput to choose the branch to checkout is presented, first element of the list is "create new branch...")
3. Press Enter. the first element is selected by default.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[vince-fugnitto]

@federicobozzini unfortunately I believe the behavior is confusing for users as the first element is not highlighted with your change but is accepted with enter. I believe it should also be highlighted.

1. start the application with a workspace under version control
2. click the branch statusbar item
3. there is no selection present
4. press enter - the create branch is triggered

For reference VS Code correctly highlights the first element in this case.

[tsmaeder]

Also consider the "gig clone" command as a test case for this fix, please. See #11900

[federicobozzini]

Closing this since a better fix was provided by #12208 .