Fix stuck notes on panic or all-notes-off.

plugins/zynaddsubfx/zynaddsubfx/src/Misc/Part.cpp

@@ -1020,6 +1020,7 @@ void Part::ComputePartSmps()
         killallnotes = 0;
         for(int nefx = 0; nefx < NUM_PART_EFX; ++nefx)
             partefx[nefx]->cleanup();
+        monomemnotes.clear();
     }
     ctl.updateportamento();
 }