This bug was originally logged at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=527510.
The log was:
Initialising audio subsystem [OpenAL]
ALSA lib pcm_dmix.c:996:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm_dmix.c:996:(snd_pcm_dmix_open) unable to open slave
AL lib: alsa.c:344: Could not open playback device 'default': No such file or directory
AL lib: oss.c:179: Could not open /dev/dsp: No such file or directory
Subsystem failed to init: ALUT:alutInit() error: There was an error opening the ALC device at src/pengine/audio.cpp:163
A possible solution would be to report this as a Warning instead.
No expert, but your solution makes sense to me.
Does this problem occur even if you disable the sound from the trigger.config file, by setting enablesound to "no"?