Fix out of bounds error in TemperatureUpdator.
Fix out of bounds error in TemperatureUpdator.

For some reason this never manifested itself before, but now, there are
times when there are no fronts and accessing things from the fronts deque
like this:

    int frntnum = ground->frontstype.size();
    ground->frontstype[frntnum-1]

will give garbage numbers, or seg fault. This commit changes code to
handle cases where ground->frontstype.size() is zero.

tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem