Bug 148626 [Regression]Can't fetch value from the filter of table/chart which inherites data from container
Steps: 1. create a table and bind a dataset in it 2. create another table/chart in the table detail/table group header 3. switch to the Filter tab in property editor 4. create a filter and select value in "<select value...>" combo 5. an error popuped up, "The expression value can't be retrieved"
chart/org.eclipse.birt.chart.reportitem.ui/src/org/eclipse/birt/chart/reportitem/ui/ReportDataServiceProvider.java
{
			return ( (DataSetHandle) list.get( 0 ) ).getQualifiedName( );
		}
		return null;
	}
	public void setContext( Object context )
	{
		itemHandle = (ExtendedItemHandle) context;
	}
	public void setDataSet( String datasetName )
	{
		boolean needClean = false;
		boolean needAddBinding = false;
		try
		{
			if ( datasetName == null )
			{
				if ( getReportDataSet( ) != null || getBoundDataSet( ) != null )
				{
					itemHandle.setDataSet( null );
					
					needClean = true;
				}
			}
			else
			{
				DataSetHandle dataset = getReportDesignHandle( ).findDataSet( datasetName );
				if ( itemHandle.getDataSet( ) != dataset )
				{
					itemHandle.setDataSet( dataset );