sfxplayer: fixes bug when using the "node argument" in SoundInterval, also fixes Py3 TypeError exception

Closes #640

direct/src/showbase/SfxPlayer.py

@@ -53,6 +53,8 @@ class SfxPlayer:
                 d = node.getDistance(listenerNode)
             else:
                 d = node.getDistance(base.cam)
+        if not cutoff:
+            cutoff = self.cutoffDistance
         if d == None or d > cutoff:
             volume = 0
         else:
@@ -70,9 +72,6 @@ class SfxPlayer:
             self, sfx, looping = 0, interrupt = 1, volume = None,
             time = 0.0, node=None, listenerNode = None, cutoff = None):
         if sfx:
-            if not cutoff:
-                cutoff = self.cutoffDistance
-
             self.setFinalVolume(sfx, node, volume, listenerNode, cutoff)
 
             # don't start over if it's already playing, unless