Bug 182673 No default value error message prompts incorrectly
Steps to reproduce: 1. New a report parameter; 2. Choose control type as Combo; 3. Choose parameter as dynamic type; Expected result: As the isRequired is false by default, parameter's default value can be null value. There should be no error message about no default value prompt. Actual result; Error messages prompts
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
}
		StructuredSelection selection = null;
		if ( index != -1 )
		{
			selection = new StructuredSelection( valueTable.getTable( )
					.getItem( index )
					.getData( ) );
		}
		else
		{
			selection = StructuredSelection.EMPTY;
		}
		valueTable.setSelection( selection );
	}
	private String[] getDataSetColumns( ScalarParameterHandle handle,
			boolean needFilter )
	{
		DataSetHandle dataSet = getDataSet( handle );
		if ( dataSet == null )
		{
			return new String[0];
		}
		CachedMetaDataHandle metaHandle = dataSet.getCachedMetaDataHandle( );
		if ( metaHandle == null )
		{
			try
			{
				metaHandle = DataSetUIUtil.getCachedMetaDataHandle( dataSet );
			}
			catch ( SemanticException e )