Fallback when value is undefined.

[rendomnet]

Clear and concise description of the problem

$t(undefined value) causes error.

Suggested solution

Fallback to "unknown" "not found" etc, when value is undefined.

Alternative

No response

Additional context

No response

Validations

• Read the Contributing Guidelines
• Read the Documentation
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.