Fixed mapserver crash (bugreport:7599)

http://hercules.ws/board/tracker/issue-7599-map-crash-july-29-latest/
Follow-up to 853489b
intif->create_pet was defined but never initialized, causing a mapserver
crash (segmentation fault) whenever a pet was created.
Thanks to jTynne for reporting it.

Signed-off-by: Haru <haru@dotalux.com>