lg-laptop: Correctly handle dmi_get_system_info() returning NULL

The laptop model is identified by parsing the product name. If no
product name is available, do not try to parse it.
Default model is 2017.

Signed-off-by: Matan Ziv-Av <matan@svgalib.org>
Link: https://lore.kernel.org/r/93ff3bb-503b-f73-bf18-87bae1699ed@svgalib.org


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>