curveguide forcefield(Kink: Braid) + particlesystem cause crash by Null Pointer in some cases.
it reported by ryu.
http://www.graphicall.org/builds/builds/showbuild.php?action=show&id=1650

in do_guides(),
do_kink(&key, &par, 0, guidetime, pd->kink_freq, pd->kink_shape, pd->kink_amp, 0.f, pd->kink, pd->kink_axis, 0, 0);
->
in do_kink(),
mul_qt_v3(par_rot, y_vec);
->
in mul_qt_v3(),
t0= -q[1]*v[0]-q[2]*v[1]-q[3]*v[2];
->
crash.