Explicitly initialize queue buffer in the main startup routine only if uIP is used.

The Rime stack already does this on its own, and there is no need to do it twice.

platform/native/contiki-main.c

@@ -199,12 +199,12 @@ main(int argc, char **argv)
 
   set_rime_addr();
 
-  queuebuf_init();
-
   netstack_init();
   printf("MAC %s RDC %s NETWORK %s\n", NETSTACK_MAC.name, NETSTACK_RDC.name, NETSTACK_NETWORK.name);
 
 #if WITH_UIP6
+  queuebuf_init();
+
   memcpy(&uip_lladdr.addr, serial_id, sizeof(uip_lladdr.addr));
 
   process_start(&tcpip_process, NULL);