6c03339e48 moved from
rtcSetNewGeometryBuffer to rtcSetSharedGeometryBuffer but kept the
additional padding of 1 element in the function call.
It was previously used for over-allocating, to allow 16-byte reads of
all accessed elements, as Embree requires.
With rtcSetSharedGeometryBuffer, this argument led to an out-of-bounds
read as memory was already allocated without padding.
float3 is already 16-bytes so there is no need for padding, hence we
remove it.
We can also note that now, even when using rtcSetSharedGeometryBuffer,
over-allocating is not needed as it's done and functional on Embree side
since v3.6.
Pull Request: https://projects.blender.org/blender/blender/pulls/129643
2f786d998d