Merge branch 'next' into raa

lib/src/upper/rlc_am.cc

@@ -315,7 +315,7 @@ int rlc_am::read_pdu(uint8_t *payload, uint32_t nof_bytes)
   // RETX if required
   if(retx_queue.size() > 0) {
     int ret = build_retx_pdu(payload, nof_bytes);
-    if (ret) {
+    if (ret > 0) {s
       pthread_mutex_unlock(&mutex);
       return ret;
     }