Work around red flashing when selecting language
Work around red flashing when selecting language

Clicking on a language from the drop down makes the text
quickly flash in red, as if there were a validation error
(see parent commit). Add a transition trick work around
these timing issues.

Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2