Fix "... is not a valid unit value" error

> I happened once when I was just adding tracks to ReaPlay, and it happened once when I changed the preference for the volume fader upper limit to +3 .
> The project had multiple ReaLearns on different tracks, all taking CC7 to output volume fader change (to the track the plugin was on).

Message: 1.1203481489865716 is not a valid unit value