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
PropertyHandle selectionChioceList = inputParameter.getPropertyHandle( ScalarParameterHandle.SELECTION_LIST_PROP );
			selectionChioceList.setValue( null );
			if ( isStatic( ) )
			{
				
				inputParameter.setValueType( DesignChoiceConstants.PARAM_VALUE_TYPE_STATIC );
				if ( !DesignChoiceConstants.PARAM_CONTROL_TEXT_BOX.equals( newControlType )
						&& !DesignChoiceConstants.PARAM_CONTROL_CHECK_BOX.equals( newControlType ) )
				{
					for ( Iterator iter = choiceList.iterator( ); iter.hasNext( ); )
					{
						SelectionChoice choice = (SelectionChoice) iter.next( );
						if ( isValidValue( choice.getValue( ) ) == null )
						{
							selectionChioceList.addItem( choice );
						}
					}
				}
				inputParameter.setDataSetName( null );
				inputParameter.setValueExpr( null );
				inputParameter.setLabelExpr( null );
			}
			else
			{
				
				inputParameter.setValueType( DesignChoiceConstants.PARAM_VALUE_TYPE_DYNAMIC );
				inputParameter.setDataSetName( dataSetChooser.getText( ) );
				inputParameter.setValueExpr( getExpression( columnChooser.getText( ) ) );