Add some assertions to ensure that arrays of correct size are used in MC

Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/marching_cubes_functors.h

@@ -226,6 +226,9 @@ void triangles_to_polygon_soup(const TriangleRange& triangles,
 
         // simply use increasing indices
         polygons.push_back({id + 2, id + 1, id + 0});
+
+        // just a safeguard against arrays of the wrong size
+        CGAL_assertion(polygons.back().size() == 3);
       }
 
 #ifdef CGAL_LINKED_WITH_TBB

Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/topologically_correct_marching_cubes_functors.h

@@ -198,6 +198,9 @@ public:
     points.insert(points.begin(), m_points.begin(), m_points.end());
     for (const auto& tri : m_triangles) {
       triangles.push_back({ tri[0], tri[1], tri[2] });
+
+      // just a safeguard against arrays of the wrong size
+      CGAL_assertion(triangles.back().size() == 3);
     }
   }