Activeae fix reliance on settings that may not be correct

While working on the darwin sink for OSX, I found an issue where we rely on settings when they may not be correct.  To reproduce, simply hook a laptop up to a device with passthrough and switch to that device.

Then unplug and restart XBMC: The passthrough setting will still be set, even though no devices allow passthrough.  The user can't fix this as the setting is (correctly) hidden.

This won't fix every case - e.g. it may be that the sink selects a device other than passthrough in a particular case, but it's better than nothing maybe?

@FernetMenta: Please feel free to school me onto where to fix it properly ;)

Second commit is a simple compile warning (signed vs unsigned) fix.