TT#14008 handle zero clock rate payload types

Specially handle zero clock rate when synthesising payload types as a
zero clock rate would have its default clock rate inserted, subsequently
messing up the clock rate tracking.

Change-Id: I8335377da5c5734d28d231c20302df2d74a15e9b

daemon/codec.c

@@ -2135,6 +2135,8 @@ static int __codec_synth_transcode_options(struct rtp_payload_type *pt, struct s
 		struct rtp_payload_type *pt_r = k->data;
 		if (g_hash_table_lookup(clockrates, GUINT_TO_POINTER(pt_r->clock_rate)))
 			continue;
+		if (pt_r->clock_rate == 0)
+			continue;
 		char *pt_s;
 		if (asprintf(&pt_s, STR_FORMAT "/%u", STR_FMT(&pt->encoding), pt_r->clock_rate) < 0)
 			continue;