add bounds checks for octaves to octave tracking “feature”

same as MirBSD commitid 10061C12BB94BB81D31

mmllib/mml.py

@@ -235,13 +235,13 @@ def mml(macro, _nplay=None, _barline=None, _mmltrk=None):
             note = 12 * octave + _MML_NAME2STEP[char]
             # octave tracking implementation
             if octave_tracking and not octave_tracking_onhold:
-                if abs(note - octave_tracking_last_note) > \
-                  abs(note + 12 - octave_tracking_last_note):
+                if (octave < 6) and (abs(note - octave_tracking_last_note) >
+                  abs(note + 12 - octave_tracking_last_note)):
                     normml[0] += ">"
                     octave += 1
                     note += 12
-                if abs(note - octave_tracking_last_note) > \
-                  abs(note - 12 - octave_tracking_last_note):
+                if (octave > 0) and (abs(note - octave_tracking_last_note) >
+                  abs((note - 12) - octave_tracking_last_note)):
                     normml[0] += "<"
                     octave -= 1
                     note -= 12