USB-Audio: the environment variable UCM_USB_PERIOD_TIME may be undefined

Fixes: 71ff24c ("USB-Audio: allow to configure period size for PCM split")
BugLink: https://github.com/alsa-project/alsa-ucm-conf/pull/240
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/ucm2/USB-Audio/USB-Audio.conf b/ucm2/USB-Audio/USB-Audio.conf
index fdc29ecc7b117b2b70362114eccd01d8ab56e13f..1c11da96c723d441359c4a03111726aa3186a9e1 100644 (file)
--- a/ucm2/USB-Audio/USB-Audio.conf
+++ b/ucm2/USB-Audio/USB-Audio.conf
@@ -7,7 +7,7 @@ Define.SplitPCMPeriodTime 10000         # 10ms
 If.env1 {
        Condition {
                Type String
-               Empty "${env:UCM_USB_PERIOD_TIME}"
+               Empty "$${env:UCM_USB_PERIOD_TIME}"
        }
        False.Define.SplitPCMPeriodTime "${env:UCM_USB_PERIOD_TIME}"
 }