ray geometries loose direction

Ray geometries will loose their direction information if the ray length is set to zero, either by calling
void RayGeom::SetLength( const double len )
with len = 0 or by calling
void RayGeom::SetPoints(const Vector3 &posStart, const Vector3 &posEnd)
with identical &posStart and &posEnd.
Ogre will show a ray with length zero with one end at posStart (and posEnd) and the other end in the middle of the screen.