Error after upgrade to php5.4

Hi,
after upgrade (my provider did it) to php5.4 i got the following Error in the backend:
Warning: Creating default object from empty value in /wp-content/plugins/wp-calendar/fsCalendarAdmin.php on line 367

how can i fix the issue?

Joerg

http://ww.wp.xz.cn/extend/plugins/wp-calendar/