Only print UE caps if DU available

The DU UE capability printing depends on data on SCS and band, which
currently is only stored with the DU. To avoid any assert, we check
that the DU is present. A follow-up commit will rework this.

openair2/RRC/NR/rrc_gNB.c

@@ -2499,10 +2499,6 @@ static void write_rrc_stats(const gNB_RRC_INST *rrc)
   {
     const gNB_RRC_UE_t *ue_ctxt = &ue_context_p->ue_context;
     f1_ue_data_t ue_data = cu_get_f1_ue_data(ue_ctxt->rrc_ue_id);
-    /* currently, we support only one DU. If we support multiple, need to
-     * search for the DU corresponding to this UE here */
-    const nr_rrc_du_container_t *du = rrc->du;
-    DevAssert(du != NULL);
 
     fprintf(f,
             "UE %d CU UE ID %d DU UE ID %d RNTI %04x random identity %016lx",
@@ -2524,7 +2520,10 @@ static void write_rrc_stats(const gNB_RRC_INST *rrc)
       fprintf(f, "    PDU session %d ID %d status %s\n", nb_pdu, pdu->param.pdusession_id, get_pdusession_status_text(pdu->status));
     }
 
-    if (ue_ctxt->UE_Capability_nr) {
+    /* currently, we support only one DU. If we support multiple, need to
+     * search for the DU corresponding to this UE here */
+    const nr_rrc_du_container_t *du = rrc->du;
+    if (du != NULL && ue_ctxt->UE_Capability_nr) {
       AssertFatal(du->setup_req->num_cells_available == 1, "only one cell supported at the moment\n");
       const f1ap_served_cell_info_t *cell_info = &du->setup_req->cell[0].info;
       fprintf(f,