get_phy_stats(): full list is non-fatal

Do not assert if the list of phy statistics is full; instead return
NULL.

In most places, this is handled appropriately (we do not store anything
if we can't). In nr_decode_pucch0(), the return value of get_phy_stats()
is used a little bit all over the function, and a constant
  if (uci_stats)
    uci_stats->variable++;
would look ugly, so make uci_stats point to the stack if we cannot store
in the phy_stats.

openair1/PHY/INIT/nr_init.c

@@ -79,8 +79,11 @@ NR_gNB_PHY_STATS_t *get_phy_stats(PHY_VARS_gNB *gNB, uint16_t rnti)
     else if (!stats->active && first_free == -1)
       first_free = i;
   }
+
+  if (first_free < 0)
+    return NULL;
+
   // new stats
-  AssertFatal(first_free >= 0, "PHY statistics list is full\n");
   stats = &gNB->phy_stats[first_free];
   stats->active = true;
   stats->rnti = rnti;

openair1/PHY/NR_TRANSPORT/pucch_rx.c

@@ -162,10 +162,15 @@ void nr_decode_pucch0(PHY_VARS_gNB *gNB,
               pucch_pdu->bit_len_harq,
               pucch_pdu->sr_flag);
 
+  /* it might be that the stats list is full: In this case, we will simply
+   * write to some memory on the stack instead of the UE's UCI stats */
+  NR_gNB_UCI_STATS_t stack_uci_stats = {0};
+  NR_gNB_UCI_STATS_t *uci_stats = &stack_uci_stats;
   NR_gNB_PHY_STATS_t *phy_stats = get_phy_stats(gNB, pucch_pdu->rnti);
-  AssertFatal(phy_stats != NULL, "phy_stats shouldn't be NULL\n");
-  phy_stats->frame = frame;
-  NR_gNB_UCI_STATS_t *uci_stats = &phy_stats->uci_stats;
+  if (phy_stats != NULL) {
+    phy_stats->frame = frame;
+    uci_stats = &phy_stats->uci_stats;
+  }
 
   int nr_sequences;
   const uint8_t *mcs;