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
{
		propertiesGroup = new Group( parent, SWT.NULL );
		propertiesGroup.setText( LABEL_GROUP_PROPERTIES );
		propertiesGroup.setLayout( new GridLayout( 2, false ) );
		propertiesGroup.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		createLabel( propertiesGroup, LABEL_PARAM_NAME, maxStrLengthProperty );
		paramNameEditor = new Text( propertiesGroup, SWT.BORDER );
		paramNameEditor.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		paramNameEditor.addModifyListener( new ModifyListener( ) {
			public void modifyText( ModifyEvent e )
			{
				valueTable.refresh( selectedParameter );
			}
		} );
		createLabel( propertiesGroup,
				LABEL_PARAMTER_PROMPT_TEXT,
				maxStrLengthProperty );
		promptText = new Text( propertiesGroup, SWT.BORDER );
		promptText.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		createLabel( propertiesGroup, LABEL_DATA_TYPE, maxStrLengthProperty );
		dataTypeChooser = new Combo( propertiesGroup, SWT.DROP_DOWN
				| SWT.READ_ONLY );
		dataTypeChooser.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		dataTypeChooser.setItems( ChoiceSetFactory.getDisplayNamefromChoiceSet( dataType ) );
		dataTypeChooser.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )
			{
				if ( selectedParameter != null
						&& selectedParameter != newParameter )
				{