Deal with empty translations

[flodolo]

Example

;Thanks for choosing the latest Firefox. <a>Now see what you can do with bookmarks</a>!


;Want to simplify your Firefox and learn how to remove buttons? <a>Get started</a>!
Chcete si zjednodušit Firefox a dozvědět se, jak odebrat některá tlačítka? <a>Podívejte se, jak na to</a>!

Note the empty translation for the first string.

langchecker will report the second string (Want to etc.) as missing, and consider ";Want to simplify etc..." as translation of the first string.

I wonder if we should do some checks, like translation can't start with ";", etc.