Fix: avoid conflict between pre-scd thread and ru thread.

openair2/LAYER2/RLC/AM_v9.3.0/rlc_am.c

@@ -551,7 +551,9 @@ rlc_am_mac_status_indication (
 
   rlc->last_absolute_subframe_status_indication = PROTOCOL_CTXT_TIME_MILLI_SECONDS(ctxt_pP);
 
-  rlc->nb_bytes_requested_by_mac = tb_sizeP;
+  if (tb_sizeP > 0) {
+    rlc->nb_bytes_requested_by_mac = tb_sizeP;
+  }
 
   status_resp.buffer_occupancy_in_bytes = rlc_am_get_buffer_occupancy_in_bytes(ctxt_pP, rlc);