Bug 141950 Selection of select value in data set filter is error
Details: Selection of select value in data set filter is error Step: 1.New a report design. 2.Create a sample datasource and dataset. 3.Switch to filter. 4.Select a value in expression. 5.Drop the list of the value1 and select <select value...> Actual result: No value is appear and pop up an error. It said that "An expression has not been set"
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
* @param dataSet
	 * @param refresh
	 * @param useColumnHints
	 *            Only applicable if the list is refreshed.
	 * @return
	 */
	public DataSetViewData[] getColumns( DataSetHandle dataSet,
			boolean refresh, boolean useColumnHints,
			boolean suppressErrorMessage )
	{
		if ( dataSet == null )
		{
			return new DataSetViewData[0];
		}
		
		DataSetViewData[] columns = (DataSetViewData[]) htColumns.get( dataSet );
		
		if ( !refresh && columns == null )
		{
			columns = getCachedColumns( dataSet );
		}
		
		
		if ( columns == null || refresh )
		{
			
			columns = null;
			try
			{