MPO: add null override list check

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

@@ -128,6 +128,7 @@ public final class Technique {
         dynamicDefines.clear();
         dynamicDefines.setAll(paramDefines);
 
+        if (overrides != null) {
             for (MatParamOverride override : overrides) {
                 if (!override.isEnabled()) {
                     continue;
@@ -139,6 +140,7 @@ public final class Technique {
                     }
                 }
             }
+        }
 
         return logic.makeCurrent(assetManager, renderManager, rendererCaps, lights, dynamicDefines);
     }