[Enhancement]: Use English text by default for missing translations in an already-supported language

[DimitriPilot3]

Checked Existing

• I have checked the repository for duplicate issues.

What enhancement would you like to see?

Currently, the fields of struct config_strings are only implicitly initialized (calling their default constructor). This means if there are any fields that aren't explicitly initialized in the struct returned by get_config_strings, for supported languages (i.e., ones that don't fall back to English), those fields will hold empty strings after the aggregate initialization in get_config_strings.

This could result in messages like the ones added recently (e.g., 686-1001 Module missing added in PR #50) not being seen at all in some languages whose translations are still in progress. Ideally, in such cases the English text should be used instead of an empty string.

Any other details to share? (OPTIONAL)

The issue was briefly mentioned in #50 (comment). I figured I should post it here to serve as a reminder before next release.