ALV GRID DISPLAY - error when downloading to local button clicked

I am using reuse_alv_grid_display to display alv report..

I am having around 90 fields to display.. some fields are large ..When i click

export-->local file.. dump error occurs..

It saying field symbol has not yet been assigned..

The termination occurred in the ABAP program "SAPLKKBL" in "GEN_FIELD_OUT2"

But When download it with few fields it's not showing error..

How can this be solved..