Since commit 12af302a last month, cards always have at least one
profile, so there is also always an active_profile (this makes the code
more simple). However, module-coreaudio-device did not create a profile
yet, causing a crash of PulseAudio when used on OS X. This patch fixes
this crash, by adding a single "On" profile. I've also added a TODO for
adding an "Off" profile which removes all sinks and sources -- I can
work on resolving this TODO later on.
