Fix leak on error.

src/persist_read_v5.c

@@ -214,6 +214,7 @@ int persist__chunk_base_msg_read_v56(FILE *db_fptr, struct P_base_msg *chunk, ui
 
 	return MOSQ_ERR_SUCCESS;
 error:
+	mosquitto__FREE(chunk->payload);
 	mosquitto__FREE(chunk->source.id);
 	mosquitto__FREE(chunk->source.username);
 	mosquitto__FREE(chunk->topic);