fire property change only if there are some listeners

Author: thurka

visualvm/core/src/org/graalvm/visualvm/core/datasupport/AsyncPropertyChangeSupport.java

@@ -66,12 +66,14 @@ public void firePropertyChange(final PropertyChangeEvent evt) {
         if (evt == null) {
             throw new NullPointerException();
         }
-        executor.submit(new Runnable() {
+        if (getPropertyChangeListeners().length>0) {
+            executor.submit(new Runnable() {
 
-            public void run() {
-                AsyncPropertyChangeSupport.super.firePropertyChange(evt);
-            }
-        });
+                public void run() {
+                    AsyncPropertyChangeSupport.super.firePropertyChange(evt);
+                }
+            });
+        }
     }
 
 }