Follow up f754643911ebb19eb68fb7b6ad1a864b02d111a8

Special Thanks to lighta for pointing out an issue with that.

Signed-off-by: shennetsind <ind@henn.et>
Fixed Bug #7325

Special Thanks to Xgear~!
http://hercules.ws/board/tracker/issue-7325-potion-pitcher-going-negative/

Signed-off-by: shennetsind <ind@henn.et>