fixed 2 possible heap overflows (inc. #1088)
GF_Box *trgr_New()
{
	ISOM_DECL_BOX_ALLOC(GF_TrackGroupBox, GF_ISOM_BOX_TYPE_TRGR);
	tmp->groups = gf_list_new();
	if (!tmp->groups) {
		gf_free(tmp);
		return NULL;
	}
	return (GF_Box *)tmp;
}

GF_Box *trgr_New()
{
	ISOM_DECL_BOX_ALLOC(GF_TrackGroupBox, GF_ISOM_BOX_TYPE_TRGR);
	tmp->groups = gf_list_new();
	if (!tmp->groups) {
		gf_free(tmp);
		return NULL;
	}
	return (GF_Box *)tmp;
}
