[dataimport] _create_copyfrom_buffer: fix separator check in string converter The empty string is a valid replace_sep. Related to #3845572

#! /bin/sh -e

if [ -x "/etc/init.d/cubicweb-ctl" ]; then
    invoke-rc.d cubicweb-ctl restart || true
fi
 
 
#DEBHELPER#
 
exit 0