fix for no sound enabled

direct/src/interval/SoundInterval.py

@@ -52,28 +52,32 @@ class SoundInterval(Interval.Interval):
         t1 = t + self.startTime
         if (t1 < 0.1):
             t1 = 0.0
-        self.sound.setVolume(self.volume)
-        self.sound.setTime(t1)
-        self.sound.setLoop(self.loop)
-        self.sound.play()
+        if self.sound != None:
+            self.sound.setVolume(self.volume)
+            self.sound.setTime(t1)
+            self.sound.setLoop(self.loop)
+            self.sound.play()
         self.state = CInterval.SStarted
         self.currT = t1
 
     def privStep(self, t):
         if self.state == CInterval.SPaused:
             # Restarting from a pause.
-            self.sound.setVolume(self.volume)
-            self.sound.setTime(t)
-            self.sound.setLoop(self.loop)
-            self.sound.play()
+            if self.sound != None:
+                self.sound.setVolume(self.volume)
+                self.sound.setTime(t)
+                self.sound.setLoop(self.loop)
+                self.sound.play()
         self.state = CInterval.SStarted
         self.currT = t
 
     def privFinalize(self):
-        self.sound.stop()
+        if self.sound != None:
+            self.sound.stop()
         self.currT = self.getDuration()
         self.state = CInterval.SFinal
 
     def privInterrupt(self):
-        self.sound.stop()
+        if self.sound != None:
+            self.sound.stop()
         self.state = CInterval.SPaused