[cairo] Bug: Crash in cairo-1.9.8

[cu]

Good one :)

Here is where this happens:
cairo-image-surface.c:2893
      int x1 = _cairo_fixed_integer_round_down (box[i].p1.x);
      int y1 = _cairo_fixed_integer_round_down (box[i].p1.y);
      int x2 = _cairo_fixed_integer_round_down (box[i].p2.x);
      int y2 = _cairo_fixed_integer_round_down (box[i].p2.y);