Bug 202891 NPE throws out when click on data item in layout[0001]
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dialogs/BindingDialogHelper.java
{
		try
		{
			IAggregationInfo info = DataUtil.getAggregationFactory( )
					.getAggrInfo( function );
			Iterator arguments = info.getParameters( ).iterator( );
			for ( ; arguments.hasNext( ); )
			{
				IParameterInfo argInfo = (IParameterInfo) arguments.next( );
				if ( argInfo.getName( ).equals( argument ) )
					return argInfo.getDisplayName( );
			}
		}
		catch ( BirtException e )
		{
			ExceptionHandler.handle( e );
		}
		return null;
	}
	public void validate( )
	{
		verifyInput( );
	}
	public boolean differs( ComputedColumnHandle binding )
	{
		if ( isAggregate( ) )
		{
			if ( !strEquals( binding.getName( ), txtName.getText( ) ) )
				return true;
			if ( !strEquals( binding.getDisplayName( ),