fix: use empty template by default when pressing enter

[elzody]

• Resolves: new file > choose template: enter key closes dialogue instead of opening new document #47320

Summary

Previously, when pressing enter without clicking on anything in the template picker, it would simply close and nothing would happen -- no document created, etc. The expected behavior is that pressing enter would just create a document based on the default, empty template. This PR makes it so that the empty template preview is focused when the picker is opened, thus pressing enter when the picker opens will now create a file based on the empty template.

2024-08-20.17-30-17.mp4

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[AndyScherzinger]

/backport to stable30

[susnux]

Thank you :)