Update ush/forecast_postdet.sh

Co-authored-by: Rahul Mahajan <aerorahul@users.noreply.github.com>

ush/forecast_postdet.sh

@@ -354,7 +354,7 @@ WW3_postdet() {
   local ww3_binary_restart_file ww3_netcdf_restart_file
   ww3_binary_restart_file="${restart_dir}/${restart_date:0:8}.${restart_date:8:2}0000.restart.ww3" 
   ww3_restart_file="${restart_dir}/${restart_date:0:8}.${restart_date:8:2}0000.restart.ww3.nc" 
-  if [[ -s "${ww3_restart_file}" ]]; then 
+  if [[ -s "${ww3_netcdf_restart_file}" ]]; then 
     export WW3_restart_from_binary=false 
     seconds=$(to_seconds "${restart_date:8:2}0000")  # convert HHMMSS to seconds
     ww3_restart_dest_file="ufs.cpld.ww3.r.${restart_date:0:4}-${restart_date:4:2}-${restart_date:6:2}-${seconds}.nc"