spoolss: fix segfault when "default devmode" is disabled
Currently when "default devmode" is explicitly disabled, and a printer
is added with a null device mode, spoolssd crashes in copy_devicemode().
Both construct_printer_info2() and construct_printer_info8() code paths
currently unconditionally attempt to copy a printers device mode,
without checking whether one is present.
This change fixes this regression such that construct_printer_info*()
functions check for a null device mode before copying.
https://bugzilla.samba.org/show_bug.cgi?id=9433
Reviewed-by: Andreas Schneider <asn@samba.org>
(cherry picked from commit
d7fdb05464a67ced7afb8dfdf0aa6be77cb84fd6)