https://github.com/alsa-project/alsa-ucm-conf/commit/b68aa52acdd2763fedad5eec0f435fbf43e5ccc6

From b68aa52acdd2763fedad5eec0f435fbf43e5ccc6 Mon Sep 17 00:00:00 2001
From: Jaroslav Kysela <perex@perex.cz>
Date: Mon, 4 Sep 2023 16:39:52 +0200
Subject: [PATCH] SplitPCM: Device argument may not be set

Link: https://github.com/alsa-project/alsa-ucm-conf/issues/346
Fixes: 10967ea ("SplitPCM: Fix Device variable in SplitPCMDevice macro")
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
--- a/ucm2/common/pcm/split.conf
+++ b/ucm2/common/pcm/split.conf
@@ -326,7 +326,7 @@ DefineMacro.SplitPCMDevice {
 	If.0 {
 		Condition {
 			Type String
-			Empty "${var:__Device}"
+			Empty "${var:-__Device}"
 		}
 		True.Define.__Device "0"
 	}