Bug in compton.c in electron velocities

[jhmatthews]

Taya Govreen-Segal raised the following issue - it looks like there's a typo in compton.c where there is some code to reverse velocities:

  if (random_number (0.0, 1.0) < 0.5 * (1. + fabs (v / VLIGHT)))
  {
    /* Then we want the photon to be headed  towards the photon */
    if (v > 0)
    {
      velocity_electron[0] = (-velocity_electron[0]);
      velocity_electron[2] = (-velocity_electron[1]);
      velocity_electron[2] = (-velocity_electron[2]);
    }
  }
  else if (v < 0)
  {
    velocity_electron[0] = (-velocity_electron[0]);
    velocity_electron[2] = (-velocity_electron[1]);
    velocity_electron[2] = (-velocity_electron[2]);
  }

where the second line of each block assigns velocity_electron[2] twice and doesn't change velocity_electron[1]. I'm a bit confused how this hasn't been picked up in tests, it seems important.