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
if ( PARAM_CONTROL_COMBO.equals( newControlType ) )
			{
				newControlType = DesignChoiceConstants.PARAM_CONTROL_LIST_BOX;
				
				inputParameter.setMustMatch( false );
			}
			else if ( PARAM_CONTROL_LIST.equals( newControlType ) )
			{
				newControlType = DesignChoiceConstants.PARAM_CONTROL_LIST_BOX;
				
				inputParameter.setMustMatch( true );
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.MUCH_MATCH_PROP,
						null );
			}
			
			inputParameter.setControlType( newControlType );
			
			if ( DesignChoiceConstants.PARAM_TYPE_DATETIME.equals( getSelectedDataType( ) ) )
			{
				defaultValue = DEUtil.convertToXMLString( DataTypeUtil.toDate( defaultValue,
						ULocale.US ) );
			}
			inputParameter.setDefaultValue( defaultValue );
			
			inputParameter.setDataType( DATA_TYPE_CHOICE_SET.findChoiceByDisplayName( dataTypeChooser.getText( ) )
					.getName( ) );