fix bug for nrows

when `header_row=0` , `n_rows` remains unchanged

Author: Euler-37

src/csv_module.F90

@@ -249,7 +249,7 @@ subroutine read_csv_file(me,filename,header_row,skip_rows,status_ok)
         end if
         if (present(header_row)) then
             iheader = max(0,header_row)
-            n_rows = n_rows - 1
+            n_rows = n_rows - merge(0,1,iheader==0)
         else
             iheader = 0
         end if