Bug: Key stuck when in unison mode with LESS than 4 voices

[tomatoKetchup]

To reproduce:

• Create a patch in unison mode and change voice count to 2 or 3
• Set "local mode" to OFF
• In a DAW, set up uFreak as MIDI IN (controller) and MIDI OUT (ext. instrument)
• Setup track with MIDI IN as uFreak KB and OUT to uFreak instrument
• Make sure both "Arp/Seq" and "Hold" buttons are off
• On the uFreak KB play and hold a key, then play another key. Release both keys: the 1st key pressed keeps playing until it is hit again
• If you do the same using another MIDI keyboard, the issue doesn't occur, so it's definitely linked to the uFreak's own keyboard

Tested in both Ableton Live and Studio One, was able to reproduce bug in both, so it's not seemingly DAW-specific.

[Carney#12]

This also happens dawless using a polyphonic step sequencer.