diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index e957c67a85..3e132ecdd6 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -360,6 +360,7 @@ class calendar_uiforms extends calendar_ui
 						break;
 
 					default:		// existing participant row
+						if (!is_array($data)) continue;	// widgets in participant tab, above participant list
 						foreach(array('uid','status','quantity','role') as $name)
 						{
 							$$name = $data[$name];