Hello!
Sorry, I can't speak und understand at all French, but I think I know what's the problem and I try it in English.

I had this problem too- please check your FR.php at the very last lines and delete all empty lines under "?>", so that now ?> is the very last line.
The problem is happening when copying the FR.txt from the addon-site here with Notepad and saving it as FR.php.

Best regards
Michael