check if selected nodes is empty

Author: neph1

jme3-scenecomposer/src/com/jme3/gde/scenecomposer/SceneComposerTopComponent.java

@@ -1321,6 +1321,9 @@ public void resultChanged(LookupEvent ev) {
     }
 
     private boolean select(AbstractSceneExplorerNode[] nodes) {
+        if( nodes.length == 0) {
+            return false;
+        }
         AbstractSceneExplorerNode first = nodes[0];
         if (editorController != null) {
             editorController.setSelectedExplorerNode(first);