Translator: keeps domain in untranslated message, vol. 2

So... I tried to implement https://github.com/Kdyby/Translation/pull/48#issuecomment-51616141

It almost works, with one problem... because of https://github.com/symfony/Translation/blob/master/Translator.php#L205 and similar line in transChoice, my NULL value from MessageCatalogue is always returned as empty string. And I don't think it's safe to assume, that returned empty string means untranslated. 

I have two possible solutions for this, but cannot decide which one to choose:
- return some special character/string from catalogue instead of null
- or just copy trans/transChoice methods from Symfony to Kdyby and make neccessary changes

What do you think? Or do you have some better idea?


hm, I've added the line, but it doesn't show up here in diffs... weird