Code review comment for lp:~charlesk/indicator-power/lp-1075192

While this looks like a worthwhile fix in its own right, I'm not sure how this fixes bug 1075192.

(a) according to your explanation in comment 4 on the bug, I should experience the same problem -- but I am not able to reproduce this at all

(b) a label should *never* be displayed, no matter how the devices are sorted

(c) with this fix, the label would still appear when there's only line power available (although we don't show the indicator in that case)