Bug 183579 Model need hold on DimensionConditionHandle and DimensionJoinConditionHandle signleton or overwrites the equals and hashcode method
The Dataset Joint Editor need join two Editparts which have the same model. But the DimensionConditionHandle and the DimensionJoinConditionHandle are create a new instance erery time when I get them. So model need hold on them signleton or overwrites the equals and hashcode method.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/MemberRef.java
* @param module
	 *            the module
	 * 
	 * @param element
	 *            the element for which to retrieve the list
	 * @return the list of structures
	 */
	public List getList( Module module, DesignElement element )
	{
		if ( propDefn.isList( ) )
		{
			
			
			List list = (ArrayList) element.getProperty( module, propDefn );
			if ( list == null )
				return null;
			switch ( refType )
			{
				case PROPERTY :
				case PROPERTY_LISTn :
					return list;
				case PROPERTY_LISTn_MEMBER :
				case PROPERTY_LISTn_MEMBER_LISTn :
					if ( !member[0].isList( ) )
						return list;
					
					
					Structure struct = getStructure( list, 0 );
					if ( struct == null )
						return null;