* Fix "particlesPerSecond set to 0 accumulates timeDiff" issue

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@9713 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/core/com/jme3/effect/ParticleEmitter.java

@@ -718,8 +718,9 @@ public class ParticleEmitter extends Geometry {
      */
     public void setParticlesPerSec(float particlesPerSec) {
         this.particlesPerSec = particlesPerSec;
+        timeDifference = 0;
     }
-
+    
     /**
      * Get the start color of the particles spawned.
      *