fix delete track regression

template/engine/sequencer.py

@@ -369,7 +369,14 @@ class SequencerInterface(_Interface): #Basically the midi part of a track.
         undo. That is why we bother setting calfboxTrack to None
         again.
         """
+        if not self.calfboxTrack: #maybe non-template part deactivated it, like Patroneo groups
+            return
+
+        try:
             portlist = cbox.JackIO.get_connected_ports(self.cboxPortName())
+        except: #port not found.
+            portlist = []
+
         self._beforeDeleteThisJackMidiWasConnectedTo = portlist
 
         self.calfboxTrack.set_external_output("")