[gPXE] fall-back filename

[Alexander Heinz]

> In regards to your challenge of testing for a populated gPXE setting:
> 
> Please try:
> 
> set taken:hex ${filename:hex}:00
> 
> instead of '${take} ${filename}'.  Feel free to let me know the results.

I just wanted to let you know that it worked.

Thank you very much!

Best regards,
Alex