Improve handling of undefined visitor data for Somaliland region

[eremannisto]

Describe the Bug

Description:
When viewing the visitor map, hovering over the Somaliland region displays "undefined: X visitors" which appears to be a raw JavaScript undefined value being rendered. While Somaliland's status as an unrecognized state may explain the lack of data, the current display looks like a technical error rather than an intentional handling of this edge case.

Suggested Solution:
Replace the "undefined" text with a more user-friendly message such as:

• "Unknown region: X visitors"
• "Unrecognized region: X visitors"
• "No data available: X visitors"

This would make it clearer that the lack of data is handled intentionally rather than showing what appears to be a JavaScript error to end users.

Database

PostgreSQL

Relevant log output

No response

Which Umami version are you using? (if relevant)

v2.13.2

Which browser are you using? (if relevant)

Chrome

How are you deploying your application? (if relevant)

Docker

[mikecao]

That makes sense. A PR would be welcome.

[eremannisto]

We should handle this with i18n in mind. We could either add new translations for all languages, or simply reuse the existing label.unknown from the locale JSON. With label.unknown it would be simpler since we wouldn't need to create new translations. I already have the necessary code changes ready for this.

Example image:

[eremannisto]

PR made 3060

[mikecao]

Fixed in v2.14.0.