[Wien] blank struct file

[tyagi at barc.gov.in]

Dear friends,

 I was trying to run some supercell calculation with a oxygen vacancy in a
tetragonal system. I tried two options.
1. Simply remove the oxygen atom.
2. Replace oxygen atom by helium.

I choose F lattice. Now after nn, sgroup and symmetry, when i tried to run
lstart, it showed the error, and as i observed that all atoms have gone
from struct file.Now only lattice parameters are there in Struct file.
I am totally confused with this error, kindly help me out even if i am
doing some obvious mistake.

Thanking you
Mohit Tyagi