msg_par_hg_tot jobs with only one resource and communication segfault

To reproduce:

{
    "nb_res": 4,
    "jobs": [
        {"id":1, "subtime":0, "res": 1, "profile": "msg_tot_test"},
    ],

    "profiles": {
        "msg_tot_test": {
            "type": "msg_par_hg_tot",
            "cpu": 1e10,
            "com": 1e7
        }
    }
}