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
{
					formatCategroy = choiceSet.findChoice( DesignChoiceConstants.NUMBER_FORMAT_TYPE_UNFORMATTED )
							.getName( );
				}
				formatPattern = null;
			}
			else
			{
				formatCategroy = selectedParameter.getCategory( );
				if ( formatCategroy == null )
				{
					formatCategroy = DesignChoiceConstants.STRING_FORMAT_TYPE_UNFORMATTED;
				}
				formatPattern = selectedParameter.getPattern( );
			}
		}
		updateFormatField( );
	}
	private String getInputDisplayName( )
	{
		String displayName = null;
		if ( DesignChoiceConstants.PARAM_CONTROL_LIST_BOX.equals( selectedParameter.getControlType( ) ) )
		{
			if ( selectedParameter.isMustMatch( ) )
			{
				displayName = DISPLAY_NAME_CONTROL_COMBO;
			}
			else
			{
				displayName = DISPLAY_NAME_CONTROL_LIST;