select channel in mixer: allow clicking on area below fader

Currently you can select a channel in the mixer either by clicking into the meter area or on the channel titel at the bottom.

Both are not ideal, if you want to hit the meter area you might accidentaly hit the fader and change the level, if you want to hit the title at the bottom you might accidentaly hit the color selection popup (right corner hover arrow).

The black area above the title (which indicates stereo/mono and has the channel number) is inactive right now, it would be a perfect space to click for channel selection. Please enable that a click in this area works for selecting a channel. Same could be for the level display (text) just below the fader.