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 static final String CHOICE_NO_DEFAULT = Messages.getString( "ParameterDialog.Choice.NoDefault" ); 
	private static final String GROUP_PROPERTIES = Messages.getString( "ParameterDialog.Group.Properties" ); 
	private static final String GROUP_MORE_OPTION = Messages.getString( "ParameterDialog.Group.MoreOption" ); 
	private static final String LABEL_NAME = Messages.getString( "ParameterDialog.Label.Name" ); 
	private static final String LABEL_DATETIME_PROMPT = Messages.getString( "ParameterDialog.Label.DateTImePrompt" ); 
	private static final String LABEL_PROMPT_TEXT = Messages.getString( "ParameterDialog.Label.PromptText" ); 
	private static final String LABEL_PARAM_DATA_TYPE = Messages.getString( "ParameterDialog.Label.DataType" ); 
	private static final String LABEL_DISPALY_TYPE = Messages.getString( "ParameterDialog.Label.DisplayType" ); 
	private static final String LABEL_DEFAULT_VALUE = Messages.getString( "ParameterDialog.Label.DefaultValue" ); 
	private static final String LABEL_HELP_TEXT = Messages.getString( "ParameterDialog.Label.HelpText" ); 
	private static final String LABEL_LIST_OF_VALUE = Messages.getString( "ParameterDialog.Label.ListOfValue" );