Bug 153523 OK button in parameter dialog is enabled without default value in combo-box
Description: OK button in parameter dialog is enabled without default value in combo-box Steps to reproduce: 1. New a report parameter, combo-box. 2. Click New button, input abc as value, click OK 3. Set abc as default value and close Edit Parameter dialog. 4. New a data source and dataset 5. Edit the parameter, remove abc value and import values from dataset Expected result: OK button is disabled for there is no default value. Actual result: OK button is enabled.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
changeDataType( dataType.findChoiceByDisplayName( dataTypeChooser.getText( ) )
							.getName( ) );
					try
					{
						selectedParameter.setDataType( dataType.findChoiceByDisplayName( dataTypeChooser.getText( ) )
								.getName( ) );
					}
					catch ( SemanticException e1 )
					{
						ExceptionHandler.handle( e1 );
					}
				}
			}
		} );
		createLabel( propertiesGroup, LABEL_DISPLAY_TYPE, maxStrLengthProperty );
		displayTypeChooser = new Combo( propertiesGroup, SWT.DROP_DOWN
				| SWT.READ_ONLY );
		displayTypeChooser.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		displayTypeChooser.setItems( new String[]{
				DISPLAY_NAME_CONTROL_LIST, DISPLAY_NAME_CONTROL_COMBO
		} );
		displayTypeChooser.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )
			{
				if ( selectedParameter != null
						&& selectedParameter != newParameter )
				{
					try
					{
						String newControlType = getSelectedDisplayType( );