fixed bug with zero area section modulus returning nans

src/libslic3r/SupportSpotsGenerator.cpp

@@ -638,6 +638,7 @@ public:
 
         auto compute_elastic_section_modulus = [&line_dir](
                 const Vec3f &centroid_accumulator, const Vec2f &second_moment_of_area_accumulator, const float &area) {
+            if (area < EPSILON) return 0.0f;
             Vec3f centroid = centroid_accumulator / area;
             Vec2f variance = (second_moment_of_area_accumulator / area
                     - centroid.head<2>().cwiseProduct(centroid.head<2>()));

src/libslic3r/SupportSpotsGenerator.hpp

@@ -10,7 +10,7 @@ namespace SupportSpotsGenerator {
 struct Params {
     // the algorithm should use the following units for all computations: distance [mm], mass [g], time [s], force [N]
     const float bridge_distance = 12.0f; //mm
-    const float bridge_distance_decrease_by_curvature_factor = 5.0f; // allowed bridge distance = bridge_distance / (this factor * (curvature / PI) )
+    const float bridge_distance_decrease_by_curvature_factor = 3.0f; // allowed bridge distance = bridge_distance / (this factor * (curvature / PI) )
 
     const float min_distance_between_support_points = 3.0f; //mm
     const float support_points_interface_radius = 0.6f; // mm