Fixed an integral type promotion problem by adding a JAS_CAST.
Modified the jpc_tsfb_synthesize function so that it will be a noop for
an empty sequence (in order to avoid dereferencing a null pointer).
void jpc_ppxstabent_destroy(jpc_ppxstabent_t *ent)
{
	if (ent->data) {
		jas_free(ent->data);
	}
	jas_free(ent);
}

void jpc_ppxstabent_destroy(jpc_ppxstabent_t *ent)
{
	if (ent->data) {
		jas_free(ent->data);
	}
	jas_free(ent);
}
