Fix crash when trying to edit a hidden track in the track editor

qtgui/scorescene.py

@@ -109,7 +109,8 @@ class GuiScore(QtWidgets.QGraphicsScene):
 
     def updateModeSingleTrackRedraw(self, nameAsString:str, trackId:int, trackExport:tuple):
         """trackExport is a tuple of block export dicts"""
-        self.tracks[trackId].updateMode(nameAsString)
+        if trackId in self.tracks: #is visible?
+            self.tracks[trackId].updateMode(nameAsString)
 
     def maxTrackLength(self):
         if self.tracks: