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/ParameterDialog.java
);
		createDataSet = new Button( composite, SWT.PUSH );
		createDataSet.setText( BUTTON_CREATE_DATA_SET );
		setButtonLayoutData( createDataSet );
		createDataSet.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )
			{
				new NewDataSetAction( ).run( );
				refreshDataSets( );
			}
		} );
		createLabel( composite, LABEL_SELECT_VALUE_COLUMN );
		columnChooser = new Combo( composite, SWT.BORDER | SWT.READ_ONLY );
		columnChooser.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		columnChooser.addSelectionListener( new SelectionAdapter( ) {
			public void widgetDefaultSelected( SelectionEvent e )
			{
				updateButtons( );
			}
		} );
		createLabel( composite, null );
		createLabel( composite, LABEL_SELECT_DISPLAY_TEXT );
		displayTextChooser = new Combo( composite, SWT.BORDER | SWT.READ_ONLY );
		displayTextChooser.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		createLabel( composite, null );
		createDefaultEditor( );
		listLimit.setEditable( true );
	}
	private void createDefaultEditor( )
	{