ACPI button: don't try to use a non-existent lid device

If a call comes in to check the lid state but there's no lid device
present, we should return -ENODEV.

Signed-off-by: Jesse Barnes <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

drivers/acpi/button.c

···
 	acpi_status status;
 	unsigned long long state;
 
+	if (!lid_device)
+		return -ENODEV;
+
 	status = acpi_evaluate_integer(lid_device->handle, "_LID", NULL,
 				       &state);
 	if (ACPI_FAILURE(status))