SDK : Material editor fixed an npe in MaterialProperty when a param value was null

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@10438 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

jme3-materialeditor/src/com/jme3/gde/materials/MaterialProperty.java

@@ -28,9 +28,11 @@ public class MaterialProperty {
     public MaterialProperty(MatParam param) {
         this.type = param.getVarType().name();
         this.name = param.getName();
-        try {
-            this.value = param.getValueAsString();
-        } catch (UnsupportedOperationException e) {
+        if (param.getValue() != null) {
+            try {
+                this.value = param.getValueAsString();
+            } catch (UnsupportedOperationException e) {
+            }
         }
     }