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
*/
	private String getSelectedControlType( )
	{
		String displayText = controlTypeChooser.getText( );
		if ( StringUtil.isBlank( displayText ) )
		{
			return getInputControlType( );
		}
		if ( DISPLAY_NAME_CONTROL_COMBO.equals( displayText ) )
		{
			return PARAM_CONTROL_COMBO;
		}
		if ( DISPLAY_NAME_CONTROL_LIST.equals( displayText ) )
		{
			return PARAM_CONTROL_LIST;
		}
		return controlType.findChoiceByDisplayName( displayText ).getName( );
	}
	private void changeDataType( )
	{
		String type = getSelectedDataType( );
		if ( type.equals( lastDataType ) )
		{
			return;
		}
		if ( buildControlTypeList( type ) )
		{
			changeControlType( );
		}
		lastDataType = type;