pootle-export

Hi Brian,

this PR fixes a minor bug in the pootle exporter script, which ignored the last key when it was untranslated. This prevented ant build-lang from auto-copying last key, considering it a valid translation when it wasn't. In turn, we'd get badly backported translations.

This one is just for fixing results of bb6bf33afa7d66866205d8d386ad0bd7ecd9e310 (see last line of so-activities-hook/docroot/WEB-INF/src/content/Language_ar.properties for example)

Next week I'll send another one with the latest translations for SO, which are currently ongoing. 

Thanks so much
Daniel.