When importing translations through Excel, any blank fields will cause the translation to become empty in the app. When running the application, these elements do not fallback to the default language text but instead show empty. This is especially annoying with text that should only contain placeholders because no data will be displayed to the user.
I personally cannot think of any use-case where a translation should be empty if there is a text in the default language. Therefor I would suggest to fallback to the default text if the translation is blank.