Negative offset should be empty but is not about clipper2

[LarsSkiba]

Further minimized example:

	Clipper2Lib::ClipperOffset offset;
	Clipper2Lib::Paths64 closedPaths = {
		{{667680768, -36382704},
		 {737202688, -87034880},
		 {742581888, -86055680},
		 {747603968, -84684800}}};

	Clipper2Lib::Paths64 solution;
	offset.AddPaths(closedPaths, Clipper2Lib::JoinType::Miter, Clipper2Lib::EndType::Polygon);
	offset.Execute(-249561088, solution);

[LarsSkiba]

7714d940ca86eb7cc8cf5f9eda2b1486daf32cb1
caused the regression

[LarsSkiba]

This tolerance does not seem to be sufficient.

if (cos_a < 0.99) path_out.push_back(path[j]); // (#405)

In this example 0.996268 does cause the issue.

[LarsSkiba]

I changed the tolerance to 0.999 which is consistent with the tolerances used in surrounding code and updated the pull request.