rtp*: guard from empty to_tag

(cherry picked from commit cdd4725)

Author: razvancrainea

modules/rtp_relay/rtp_relay_ctx.c

@@ -1633,9 +1633,9 @@ static void rtp_relay_fill_dlg(struct rtp_relay_ctx *ctx, str *dlg_callid,
 		LM_ERR("could not store dialog callid in context\n");
 	if (callid && !ctx->callid.len &&  shm_str_sync(&ctx->callid, callid) < 0)
 		LM_ERR("could not store callid in context\n");
-	if (from_tag && !ctx->from_tag.s && shm_str_sync(&ctx->from_tag, from_tag) < 0)
+	if (from_tag && from_tag->len && !ctx->from_tag.s && shm_str_sync(&ctx->from_tag, from_tag) < 0)
 		LM_ERR("could not store from tag in context\n");
-	if (to_tag && !ctx->to_tag.s && shm_str_sync(&ctx->to_tag, to_tag) < 0)
+	if (to_tag && to_tag->len && !ctx->to_tag.s && shm_str_sync(&ctx->to_tag, to_tag) < 0)
 		LM_ERR("could not store to tag in context\n");
 }
 

modules/rtpengine/rtpengine.c

@@ -4389,7 +4389,7 @@ static bencode_item_t *rtpengine_api_copy_op(struct rtp_relay_session *sess,
 		bencode_list_add_string(list, "all");
 	} else if (copy_flags & RTP_COPY_LEG_CALLER && sess->from_tag) {
 		bencode_dictionary_add_str(dict, "from-tag", sess->from_tag);
-	} else if (sess->to_tag) {
+	} else if (sess->to_tag && sess->to_tag->len) {
 		bencode_dictionary_add_str(dict, "from-tag", sess->to_tag);
 	}
 	msg = (sess->msg?sess->msg:get_dummy_sip_msg());