When size pressure is enabled, the radius may not be enough to sample
any vertices to calculate the area normal. This lead to a vector 0 plane
and a division by 0 when calculating the signed distance to the plane,
which produces a NaN that was being written to the vertex coordinates.
Reviewed By: brecht
Maniphest Tasks: T72006
Differential Revision: https://developer.blender.org/D6326
e77fdc62b7