int jpc_tsfb_synthesize(jpc_tsfb_t *tsfb, jas_seq2d_t *a)
{
	return (tsfb->numlvls > 0 && jas_seq2d_size(a)) ?
	  jpc_tsfb_synthesize2(tsfb,
	  jas_seq2d_getref(a, jas_seq2d_xstart(a), jas_seq2d_ystart(a)),
	  jas_seq2d_xstart(a), jas_seq2d_ystart(a), jas_seq2d_width(a),
	  jas_seq2d_height(a), jas_seq2d_rowstep(a), tsfb->numlvls - 1) : 0;
}
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.