ModelGeometry division by 0.0 for a single ellipsoid shape

[Maciej Komosinski]

For the following structure/genotype:

Simulator.print(ModelGeometry.forModel(Model.newFromString("//0\np:sh=1\n")).area());

in externalAreaOfSurface(), in the second iteration of

	while (surface.tryGetNext(point))

In function

void MeshBuilder::EllipsoidSurface::findNextAreaEdgeAndPhase()

There is div by 0.0 (invalid FP operation) because edge.x and edge.z are 0.0:

limit.z = edge.z*edge.z / sqrt(edge.x*edge.x + edge.z*edge.z);