Memory leak when constructing a hull from 4 vertices (tetrahedron)

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When using Valgrind memory analyzer to test a project creating convex hulls from only 4 vertices it reported issues like this (this is from a test reproducing the issue):

0 bytes in 1 blocks are definitely lost in loss record 1 of 1
  in main in /path/main.c:18
  1: malloc in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so
  2: convhull_3d_build_alloc in /path/convhull_3d/convhull_3d.h:733
  3: convhull_3d_build in /path/convhull_3d/convhull_3d.h:573
  4: main in /path/main.c:18

Code generating the report above:

int main()
{
    ch_vertex vertices[4] =
    {
        { 0,  0, -1 },
        {-1, -1,  1 },
        {-1,  1,  1 },
        { 1,  0,  1 }
    };

    int nVertices = 4;
    int* faceIndices = NULL;
    int nFaces;

    convhull_3d_build(vertices, nVertices, &faceIndices, &nFaces);

    free(faceIndices);
}

Generated convex hulls (tetrahedrons) are ok.