tm_driver crashes with segfault at random intervals

[Ben-Nivo]

The tm_driver package can occasionally crash due to a segmentation fault. This seems to happen at random moments and even when the robot is idle.

[Ben-Nivo]

After further testing, it seems that #4 does not fully solve the problem. Segmentation faults do appear to be less frequent, but still happen occasionally.

EDIT: I found a 2nd place where a race condition could cause memory corruption. I'm going to let it run in Valgrind for several days, and if no memory errors are reported I'll submit an updated pull request.