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/db/s/namespace_metadata_change_notifications.cpp:79: INVALIDATE_ITERATOR 169043 Calling "find" with element "token->nss" returns the end iterator.
/src/mongo/db/s/namespace_metadata_change_notifications.cpp:79: INVALIDATE_ITERATOR 169043 Assigning: "mapIt" = "this->_notificationsList.find(token->nss)".
/src/mongo/db/s/namespace_metadata_change_notifications.cpp:80: INVALIDATE_ITERATOR 169043 Dereferencing iterator "mapIt" though it is already past the end of its container.