plugin: Use the json_add_secret wrapper to add the shared_secret

This was incorrectly handled before, hence the wrapper which checks
correctness of the arguments.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

lightningd/peer_htlcs.c

@@ -721,7 +721,7 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
 	}
 
 	json_add_hex_talarr(s, "next_onion", p->next_onion);
-	json_add_hex(s, "shared_secret", &hin->shared_secret, sizeof(hin->shared_secret));
+	json_add_secret(s, "shared_secret", hin->shared_secret);
 	json_object_end(s);
 
 	json_object_start(s, "htlc");

wallet/test/run-wallet.c

@@ -254,6 +254,11 @@ void json_add_num(struct json_stream *result UNNEEDED, const char *fieldname UNN
 void json_add_s32(struct json_stream *result UNNEEDED, const char *fieldname UNNEEDED,
 		  int32_t value UNNEEDED)
 { fprintf(stderr, "json_add_s32 called!\n"); abort(); }
+/* Generated stub for json_add_secret */
+void json_add_secret(struct json_stream *response UNNEEDED,
+		     const char *fieldname UNNEEDED,
+		     const struct secret *secret UNNEEDED)
+{ fprintf(stderr, "json_add_secret called!\n"); abort(); }
 /* Generated stub for json_add_short_channel_id */
 void json_add_short_channel_id(struct json_stream *response UNNEEDED,
 			       const char *fieldname UNNEEDED,