limit internal pitches to 0 to 127. They can be reached through the GUI and need protection logic

engine/pattern.py

@@ -395,6 +395,10 @@ class Pattern(object):
 
             velocity = noteDict["velocity"]
             pitch = self._cachedTransposedScale[noteDict["pitch"] + scaleTransposition] + halftoneTransposition
+            if pitch > 127:
+                pitch = 127
+            elif pitch < 0:
+                pitch = 0
             exportPattern += cbox.Pattern.serialize_event(startTick, 0x90 + self.parentTrack.midiChannel, pitch, velocity) # note on
             exportPattern += cbox.Pattern.serialize_event(endTick-1, 0x80 + self.parentTrack.midiChannel, pitch, velocity) # note off  #-1 ticks to create a small logical gap. Does not affect next note on.