Bug 166315 Combo box doesn't allow blank when set string type in parameter editor
Combo box doesn't allow blank when set string type in parameter editor Steps to reproduce: 1.New a parameter, display type is Combo Box 2.Select data type as String Expected result: "Allow blank values" is enable. Actual result: "Allow blank values" is gray and can't be checked.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
return false;
	}
	private void popupFormatBuilder( boolean refresh )
	{
		String type = getSelectedDataType( );
		int style;
		if ( DesignChoiceConstants.PARAM_TYPE_BOOLEAN.equals( type ) )
		{
			return;
		}
		if ( DesignChoiceConstants.PARAM_TYPE_STRING.equals( type ) )
		{
			style = FormatBuilder.STRING;
		}
		else if ( DesignChoiceConstants.PARAM_TYPE_DATETIME.equals( type ) )
		{
			style = FormatBuilder.DATETIME;
		}
		else
		{
			style = FormatBuilder.NUMBER;
		}
		FormatBuilder formatBuilder = new FormatBuilder( style );
		formatBuilder.setInputFormat( formatCategroy, formatPattern );
		formatBuilder.setPreviewText( defaultValue );
		if ( formatBuilder.open( ) == OK )
		{
			formatCategroy = ( (String[]) formatBuilder.getResult( ) )[0];
			formatPattern = ( (String[]) formatBuilder.getResult( ) )[1];
			updateFormatField( );