Fix a enb crash when no more users could be added into the bearer manager map.

This was caused by not removing old user from the map, so add the code to cleanup the map on user removal.

lib/src/common/bearer_manager.cc

@@ -117,7 +117,11 @@ void enb_bearer_manager::add_eps_bearer(uint16_t rnti, uint8_t eps_bearer_id, sr
   auto user_it = users_map.find(rnti);
   if (user_it == users_map.end()) {
     // add empty bearer map
-    auto p  = users_map.insert(rnti, srsran::detail::ue_bearer_manager_impl{});
+    auto p = users_map.insert(rnti, srsran::detail::ue_bearer_manager_impl{});
+    if (!p) {
+      logger.error("Bearers: Unable to add a new bearer map for rnti=0x%x", rnti);
+      return;
+    }
     user_it = p.value();
   }
 
@@ -149,7 +153,14 @@ void enb_bearer_manager::remove_eps_bearer(uint16_t rnti, uint8_t eps_bearer_id)
 
 void enb_bearer_manager::rem_user(uint16_t rnti)
 {
+  auto user_it = users_map.find(rnti);
+  if (user_it == users_map.end()) {
+    logger.error("Bearers: No EPS bearer registered for rnti=0x%x", rnti);
+    return;
+  }
+
   logger.info("Bearers: Removed rnti=0x%x from EPS bearer manager", rnti);
+  users_map.erase(user_it);
 }
 
 bool enb_bearer_manager::has_active_radio_bearer(uint16_t rnti, uint32_t eps_bearer_id)