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/ParameterDialog.java
private void refreshColumns( boolean onlyFilter )
	{
		if ( columnChooser == null )
		{
			return;
		}
		if ( !onlyFilter )
		{
			DataSetHandle dataSetHandle = getDataSetHandle( );
			try
			{
				columnList = DataUtil.getColumnList( dataSetHandle );
			}
			catch ( SemanticException e )
			{
				ExceptionHandler.handle( e );
			}
			displayTextChooser.removeAll( );
			displayTextChooser.add( NONE_DISPLAY_TEXT );
			for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )
			{
				displayTextChooser.add( ( (ResultSetColumnHandle) iter.next( ) ).getColumnName( ) );
			}
			displayTextChooser.setText( NONE_DISPLAY_TEXT );
		}
		String originalSelection = columnChooser.getText( );
		columnChooser.removeAll( );
		for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )
		{
			ResultSetColumnHandle cachedColumn = (ResultSetColumnHandle) iter.next( );