Fix CU to not contain the pointer for MAC/RLC stats

Segmentation fault occured since the commit ID 9e5c5497ab,
where we try to copy the pointer which was not even been allocated. Before, we were
copying the address of a NULL pointer and therefore no segmentation fault.

This commit fixes the segmentation fault by checking if the memory was allocated, i.e. should not be
in the case of CU (as it doesn't contain MAC/RLC layers).

openair2/E2AP/RAN_FUNCTION/O-RAN/ran_func_kpm.c

@@ -115,7 +115,9 @@ static cudu_ue_info_pair_t fill_ue_related_info(arr_ue_id_t* arr_ue_id, const si
 
   if (arr_ue_id->ue_id[ue_idx].type == GNB_UE_ID_E2SM) {
     ue_info.rrc_ue_id = *arr_ue_id->ue_id[ue_idx].gnb.ran_ue_id;  // rrc_ue_id
+    if (arr_ue_id->ue_info_list != NULL) {
       ue_info.ue = arr_ue_id->ue_info_list[ue_idx];
+    }
   } else if (arr_ue_id->ue_id[ue_idx].type == GNB_CU_UP_UE_ID_E2SM) {
     /* in OAI implementation, CU-UP ue id = CU-CP ue id
                            => CU-UP ue id = rrc_ue_id, but it should not be the case by the spec */