fix bugs in share class

lib/share.php

@@ -130,7 +130,7 @@ class OC_Calendar_Share{
 		}else{
 			$string = OC_Calendar_Object::find($id);
 		}
-		$string = sha1($string);
+		$string = sha1($string['calendardata']);
 		$id = sha1($id);
 		$array = array($uniqid,$string,$id);
 		shuffle($array);
@@ -245,5 +245,6 @@ class OC_Calendar_Share{
                 $event = $result_event->fetchRow();
                 $return ['id'] = $event['eventid'];
             }
+			return $return;
         }
 }

share.php

@@ -18,4 +18,6 @@ if($shared['type'] == OC_Calendar_Share::CALENDAR){
 	header('Content-Type: text/Calendar');
 	header('Content-Disposition: inline; filename=' . $data['summary'] . '.ics'); 
 	echo $data['calendardata'];
+}else{
+	header('Error 404: Not Found');
 }