select/cray: better resiliency against bad nodes

This lets the select/cray code deal more gracefully with bad nodes:
 * avoid sscanf(NULL, ...) in basil_geometry();
 * avoid fatal() if node_ptr->name[0] == '\0'.

The other three functions,
 * basil_node_ranking(),
 * basil_get_initial_state(), and
 * basil_inventory()
rely on find_node_record() to return NULL on finding a bad node - which will
trigger an error condition, but not cause the program to abort.