Loopy Pro and Helium issue

I know “what”, but I don’t know “how”.
I’ve got one track with the contents in Helium inside the LP. If Loopy is playing and I press the play/stop button, the currently playing note doesn’t end and plays endlessly. The short solution is to press Mute on the instrument channel, but there must (should) be a more efficient way. Something like “Send all notes off to all MIDI receivers when I press stop in the transport bar”.
PS: Unfortunately I don’t have any other AU host app or MIDI player to try a combination other than LP+Helium where I can check this issue.