diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index 033f5ad661..025bdf80ea 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -310,7 +310,7 @@ class calendar_uiforms extends calendar_ui
 							break;
 
 						case 'resource':
-							if (is_array($data) && isset($data['current']) )
+							if (is_array($data))	// if $data['current'] is NOT set --> $app==''
 							{
 								list($app,$id) = explode(':',$data['current']);
 							}