Using invalid iterator

Undefined behavior may result; the program may crash or subtly misbehave. An invalid or past-the-end iterator is being used
/src/mongo/client/connpool.cpp:487: INVALIDATE_ITERATOR 155588 Calling "find" with element "host" returns the end iterator.
/src/mongo/client/connpool.cpp:487: INVALIDATE_ITERATOR 155588 Assigning: "<temporary>" = "this->_pools.find(mongo::DBConnectionPool::PoolKey(host, timeout))".
/src/mongo/client/connpool.cpp:487: INVALIDATE_ITERATOR 155588 Dereferencing iterator "this->_pools.find(mongo::DBConnectionPool::PoolKey(host, timeout))" though it is already past the end of its container.