Fixed NPE and ConcurrentModificationException during cloning TechniqueDef.

jme3-core/src/main/java/com/jme3/material/ShaderGenerationInfo.java

@@ -190,7 +190,13 @@ public class ShaderGenerationInfo implements Savable, Cloneable {
 
     @Override
     protected ShaderGenerationInfo clone() throws CloneNotSupportedException {
-        ShaderGenerationInfo clone = (ShaderGenerationInfo) super.clone();
+        final ShaderGenerationInfo clone = (ShaderGenerationInfo) super.clone();
+        clone.attributes = new ArrayList<>();
+        clone.vertexUniforms = new ArrayList<>();
+        clone.fragmentUniforms = new ArrayList<>();
+        clone.fragmentGlobals = new ArrayList<>();
+        clone.unusedNodes = new ArrayList<>();
+
 
         for (ShaderNodeVariable attribute : attributes) {
             clone.attributes.add(attribute.clone());

jme3-core/src/main/java/com/jme3/material/TechniqueDef.java

@@ -801,6 +801,7 @@ public class TechniqueDef implements Savable, Cloneable {
         clone.paramToDefineId.putAll(paramToDefineId);
 
         if (shaderNodes != null) {
+            clone.shaderNodes = new ArrayList<>();
             for (ShaderNode shaderNode : shaderNodes) {
                 clone.shaderNodes.add(shaderNode.clone());
             }