Renamed some variables forgotten when adding the battleground interface

- Follow-up to 35c131c
- Fixes bugreport:7721, thanks to purityz, Dastgir Pojee
  http://hercules.ws/board/tracker/issue-7721-lastest-update-make-map-crashing-on-battleground/

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