sony-laptop: potential null dereference

In the original code, if "device_enum" was NULL then it would
dereference it when it printed the error message.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NMatthew Garrett <mjg@redhat.com>

drivers/platform/x86/sony-laptop.c

@@ -1311,7 +1311,11 @@ static void sony_nc_rfkill_setup(struct acpi_device *device)
 	}
 
 	device_enum = (union acpi_object *) buffer.pointer;
-	if (!device_enum || device_enum->type != ACPI_TYPE_BUFFER) {
+	if (!device_enum) {
+		pr_err(DRV_PFX "No SN06 return object.");
+		goto out_no_enum;
+	}
+	if (device_enum->type != ACPI_TYPE_BUFFER) {
 		pr_err(DRV_PFX "Invalid SN06 return object 0x%.2x\n",
 				device_enum->type);
 		goto out_no_enum;