TT#14008 avoid duplicate bencode dict keys

Multiple untagged monologues can exist at the same time which would lead
to a broken bencode dictionary. Instead use a pseudo label to
distinguish them.

Change-Id: I0f41c42df8ec17c1c4fb5cc6451ea039612e505f
(cherry picked from commit 6f0439daf3)

daemon/call_interfaces.c

@@ -1745,7 +1745,13 @@ static void ng_stats_monologue(bencode_item_t *dict, const struct call_monologue
 	if (!dict)
 		goto stats;
 
-	sub = bencode_dictionary_add_dictionary(dict, ml->tag.s ? : "");
+	if (ml->tag.len)
+		sub = bencode_dictionary_add_dictionary(dict, ml->tag.s);
+	else {
+		char *buf = bencode_buffer_alloc(dict->buffer, 32);
+		snprintf(buf, 32, "<untagged %u>", ml->unique_id);
+		sub = bencode_dictionary_add_dictionary(dict, buf);
+	}
 
 	bencode_dictionary_add_str(sub, "tag", &ml->tag);
 	if (ml->viabranch.s)