Bugfix: fixed an issue that caused NPE to be raised when UnsupportedConstraint was allocated.

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@10861 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/blender/com/jme3/scene/plugins/blender/constraints/definitions/ConstraintDefinition.java

@@ -48,7 +48,7 @@ public abstract class ConstraintDefinition {
             }
         }
         this.blenderContext = blenderContext;
-        constraintHelper = blenderContext.getHelper(ConstraintHelper.class);
+        constraintHelper = (ConstraintHelper) (blenderContext == null ? null : blenderContext.getHelper(ConstraintHelper.class));
         this.ownerOMA = ownerOMA;
     }