CHECK that ThreadPool is given a positive num_threads (#1800)
CHECK that ThreadPool is given a positive num_threads (#1800)

Signed-off-by: Mac Mason <347ead6348e936507920c15d2ae8266ac6ce9b49@kingseye.net>
wohe/cartographer,googlecartographer/cartographer,googlecartographer/cartographer,wohe/cartographer,googlecartographer/cartographer,wohe/cartographer,cartographer-project/cartographer,googlecartographer/cartographer,wohe/cartographer,cartographer-project/cartographer,cartographer-project/cartographer,cartographer-project/cartographer