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
String newControlType = getSelectedControlType( );
			if ( PARAM_CONTROL_COMBO.equals( newControlType ) )
			{
				newControlType = DesignChoiceConstants.PARAM_CONTROL_LIST_BOX;
				inputParameter.setMustMatch( true );
			}
			else if ( PARAM_CONTROL_LIST.equals( newControlType ) )
			{
				newControlType = DesignChoiceConstants.PARAM_CONTROL_LIST_BOX;
				inputParameter.setMustMatch( false );
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.MUCH_MATCH_PROP,
						null );
			}
			
			inputParameter.setControlType( newControlType );
			
			inputParameter.setDefaultValue( defaultValue );
			
			inputParameter.setDataType( dataType.findChoiceByDisplayName( dataTypeChooser.getText( ) )
					.getName( ) );
			
			PropertyHandle selectionChioceList = inputParameter.getPropertyHandle( ScalarParameterHandle.SELECTION_LIST_PROP );
			selectionChioceList.setValue( null );
			if ( isStatic( ) )
			{
				
				inputParameter.setValueType( DesignChoiceConstants.PARAM_VALUE_TYPE_STATIC );