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
{
	private static final String LABEL_PARAMTER_PROMPT_TEXT = Messages.getString( "CascadingParametersDialog.Label.parameterPromptText" ); 
	private static final String LABEL_VALUES = Messages.getString( "CascadingParametersDialog.Label.values" ); 
	private static final String LABEL_GROUP_GENERAL = Messages.getString( "CascadingParametersDialog.Label.group.general" ); 
	private static final String LABEL_CASCADING_PARAMETER_NAME = Messages.getString( "CascadingParametersDialog.Label.cascadingParam.name" ); 
	private static final String LABEL_GROUP_PROMPT_TEXT = Messages.getString( "CascadingParametersDialog.Label.groupPromptText" );