Quick-fix new generateMessageFiles()

[andywer]

Seems like the latest feature's code has a bug. The output JS file that we create might end up empty.

[andywer]

@carestad Maybe you have a quick fix at hand?

And a bit of shame on me that I didn't notice when reviewing 😉

[carestad]

Oh! Well, I suppose moving the two lines below the if (key_exists()) into the if there would do the trick. Let me fix :)