enb: fix warning when removing user

when removing a user from the eNB we iterated over all possible LCIDs
and set the buffer state to zero in the scheduler.

this resulted in following log entries:

13:57:23.856334 [RRC ] [I] Received Release Complete rnti=0x46
13:57:23.856352 [MAC ] [W] [ 5149] The provided lcid=6 is not valid
13:57:23.856362 [MAC ] [W] [ 5149] The provided lcid=7 is not valid
13:57:23.856368 [MAC ] [W] [ 5149] The provided lcid=8 is not valid
13:57:23.856371 [MAC ] [W] [ 5149] The provided lcid=9 is not valid
13:57:23.856376 [MAC ] [W] [ 5149] The provided lcid=10 is not valid

we now check if the bearer exits at RLC and only report those to the MAC.

srsenb/src/stack/upper/rlc.cc

@@ -91,7 +91,9 @@ void rlc::clear_buffer(uint16_t rnti)
   if (users.count(rnti)) {
     users[rnti].rlc->empty_queue();
     for (int i = 0; i < SRSLTE_N_RADIO_BEARERS; i++) {
-      mac->rlc_buffer_state(rnti, i, 0, 0);
+      if (users[rnti].rlc->has_bearer(i)) {
+        mac->rlc_buffer_state(rnti, i, 0, 0);
+      }
     }
     log_h->info("Cleared buffer rnti=0x%x\n", rnti);
   }