Fixed an issue that prevented the preview to be displayed properly in the material editor

sdk/jme3-materialeditor/src/com/jme3/gde/materials/MaterialPreviewRenderer.java

@@ -142,6 +142,7 @@ public class MaterialPreviewRenderer implements SceneListener {
     }
 
     private int lastErrorHash = 0;
+
     private void smartLog(String expText, String message) {
         int hash = message.hashCode();
         if (hash != lastErrorHash) {
@@ -160,7 +161,9 @@ public class MaterialPreviewRenderer implements SceneListener {
             for (MatParam matParam : mat.getParams()) {
                 dummy.setParam(matParam.getName(), matParam.getVarType(), matParam.getValue());
             }
+            if (mat.getActiveTechnique() != null) {
                 dummy.selectTechnique(mat.getActiveTechnique().getDef().getName(), SceneApplication.getApplication().getRenderManager());
+            }
             dummy.getAdditionalRenderState().set(mat.getAdditionalRenderState());
 
             //creating a dummy geom and assigning the dummy material to it
@@ -183,6 +186,8 @@ public class MaterialPreviewRenderer implements SceneListener {
             return null;
         } catch (NullPointerException npe) {
             //utterly bad, but for some reason I get random NPE here and can't figure out why so to avoid bigger issues, I just catch it.
+            //the printStackTrace is intended, it will show up in debug mode, but won't be displayed in standzrd mode
+            npe.printStackTrace();
             return null;
         }
 
@@ -191,7 +196,6 @@ public class MaterialPreviewRenderer implements SceneListener {
         return dummy;
     }
 
-    
     public void switchDisplay(DisplayType type) {
         switch (type) {
             case Box:

sdk/jme3-materialeditor/src/com/jme3/gde/materials/multiview/widgets/MaterialPreviewWidget.java

@@ -10,29 +10,9 @@
  */
 package com.jme3.gde.materials.multiview.widgets;
 
-import com.jme3.asset.DesktopAssetManager;
-import com.jme3.asset.MaterialKey;
 import com.jme3.gde.core.assets.ProjectAssetManager;
-import com.jme3.gde.core.scene.PreviewRequest;
-import com.jme3.gde.core.scene.SceneApplication;
-import com.jme3.gde.core.scene.SceneListener;
 import com.jme3.gde.core.scene.SceneRequest;
 import com.jme3.gde.materials.MaterialPreviewRenderer;
-import com.jme3.material.MatParam;
-import com.jme3.material.Material;
-import com.jme3.math.FastMath;
-import com.jme3.math.Quaternion;
-import com.jme3.math.Vector3f;
-import com.jme3.renderer.RendererException;
-import com.jme3.scene.Geometry;
-import com.jme3.scene.shape.Box;
-import com.jme3.scene.shape.Quad;
-import com.jme3.scene.shape.Sphere;
-import com.jme3.util.MaterialDebugAppState;
-import com.jme3.util.TangentBinormalGenerator;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-import javax.swing.ImageIcon;
 
 /**
  *