Alert translations are not used

The translations from alert.po don't seem to be used (only the ones from trivabble.po).

Steps to reproduce:

• start or continue a game
• change "interface language" to "English"
• click the button: "Put back all the tiles in the bag"
• observe that the question is in English (as expected), but the buttons are in French.

• Expected: the answers are in the interface language
• Actual: the answers are in French