Bug 145478 Unable "Select Value" in the Join data set's filter
Step to reproduce: 1.new a join data set(please use the attached file) 2.right click the dataset and click the Edit 3.go to the Filter pane and set a filer 4.click the list of Value1 Actual result: A warning pop up and cant select Value.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
/**
	 * @return
	 */
	private static DataSetProvider newInstance( )
	{
		return new DataSetProvider( );
	}
	/**
	 * 
	 * @return
	 */
	public static DataSetProvider getCurrentInstance( )
	{
		if ( instance == null )
			instance = newInstance( );
		return instance;
	}
	/**
	 * get columns data by data set name
	 * @param dataSetName
	 * @param refresh
	 * @return
	 */
	public DataSetViewData[] getColumns( String dataSetName, boolean refresh )
	{
		ModuleHandle handle = Utility.getReportModuleHandle( );
		DataSetHandle dataSet = handle.findDataSet( dataSetName );
		if ( dataSet == null )
		{
			return new DataSetViewData[]{};