Code review comment for lp:~binli/unity-control-center/1291862

With this patch, I noticed that if you have multiple inputs (> 1) then the slider is made insensitive when you remove one of them, meaning that you can't update the remaining input's volume.

There's a similar piece of code for adding inputs and outputs that only fires if it's the first one - it makes sense to do that check here too, and fixes that bug. You only need to consider making the slider insensitive if we are handling the removal of the last input.

I did this in lp:~laney/unity-control-center/make-insensitive-on-last-removal-only - please have a look and consider merging into this branch.