R1:3487ee444a88

Fix regression in new confirmation Dialog

Summary:
Fix a JavaScript regression encapsulating the problematic part into an `if`.

Other minor changes:

- dedicate a variable for the confirmation messages to improve i18n in the future (but also to avoid 80 characters and make lint happy)
- replace `confirm` with `window.confirm` (to make lint happy)

Ref T15034
Ref D25015

Test Plan:
- surf on your local Phorge
- no JavaScript errors in console

Reviewers: bekay, Ekubischta, O1 Blessed Committers, avivey…