Error when validating model that has attribute

What steps will reproduce the problem?
1. Create any class with any name
2. Add an Attribute with any name and type to that class
3. Click on "Validate"

What is the expected output? What do you see instead?
Expected to open the console with the error messages or just the "Model 
validated successfuly". From version 0.6 on it does not show anything, even if 
one opens the console window. Running in eclipse we notice an exception. 

Please use labels and text to provide additional information.
Exception in Eclipse:
Caused by: java.lang.ClassCastException: 
org.eclipse.ocl.ecore.internal.OCLStandardLibraryImpl$1 cannot be cast to 
RefOntoUML.Property
    at RefOntoUML.impl.PropertyImpl.basicGetOpposite(PropertyImpl.java:599)
    at RefOntoUML.impl.PropertyImpl.eIsSet(PropertyImpl.java:1359)
    at org.eclipse.emf.ecore.impl.BasicEObjectImpl.eIsSet(BasicEObjectImpl.java:1237)
    at org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.hasNext(EContentsEList.java:401)
    at org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.next(EContentsEList.java:559)
    at org.eclipse.emf.ecore.util.EObjectValidator.validate_EveryReferenceIsContained(EObjectValidator.java:784)
    at RefOntoUML.util.RefOntoUMLValidator.validateProperty(RefOntoUMLValidator.java:2122)
    at RefOntoUML.util.RefOntoUMLValidator.validate(RefOntoUMLValidator.java:987)
    at org.eclipse.emf.ecore.util.EObjectValidator.validate(EObjectValidator.java:324)
    at org.eclipse.emf.ecore.util.Diagnostician.validate(Diagnostician.java:159)
    at org.eclipse.emf.ecore.util.Diagnostician.validate(Diagnostician.java:137)

(...)

Original issue reported on code.google.com by vmsob...@gmail.com on 11 Jun 2013 at 9:29

Lucieneg / ontouml-lightweight-editor

Error when validating model that has attribute #15