Fix error when loading a particle effect in particle panel

direct/src/tkpanels/ParticlePanel.py

@@ -19,6 +19,8 @@ import Pmw, os,Placer
 
 from panda3d.core import *
 from panda3d.physics import *
+from panda3d.direct import getParticlePath
+
 
 class ParticlePanel(AppShell):
     # Override class variables