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>

drivers/platform/x86/lg-laptop.c

@@ -655,7 +655,7 @@ static int acpi_add(struct acpi_device *device)
 		goto out_platform_registered;
 	}
 	product = dmi_get_system_info(DMI_PRODUCT_NAME);
-	if (strlen(product) > 4)
+	if (product && strlen(product) > 4)
 		switch (product[4]) {
 		case '5':
 		case '6':