fix: backport assimp PR 6283

[c-dilks]

apply backport of assimp/assimp#6283

resolves cadmesh build errors

/opt/mlibrary/cadmesh/external/assimp/code/AssetLib/X3D/X3DGeoHelper.cpp: In static member function ‘static void Assimp::X3DGeoHelper::coordIdx_str2lines_arr(const std::vector<int>&, std::vector<aiFace>&)’:
/opt/mlibrary/cadmesh/external/assimp/code/AssetLib/X3D/X3DGeoHelper.cpp:194:20: error: array subscript -1 is outside array bounds of ‘int [2305843009213693951]’ [-Werror=array-bounds=]
  194 |     if (f_data.back() != (-1)) {
      |         ~~~~~~~~~~~^~
In file included from /usr/include/c++/15.2.1/x86_64-pc-linux-gnu/bits/c++allocator.h:33,
                 from /usr/include/c++/15.2.1/bits/allocator.h:46,
                 from /usr/include/c++/15.2.1/string:45,
                 from /opt/mlibrary/cadmesh/external/assimp/include/assimp/types.h:78,
                 from /opt/mlibrary/cadmesh/external/assimp/code/AssetLib/X3D/X3DGeoHelper.h:6,
                 from /opt/mlibrary/cadmesh/external/assimp/code/AssetLib/X3D/X3DGeoHelper.cpp:1:
In member function ‘_Tp* std::__new_allocator<_Tp>::allocate(size_type, const void*) [with _Tp = int]’,
    inlined from ‘static _Tp* std::allocator_traits<std::allocator<_CharT> >::allocate(allocator_type&, size_type) [with _Tp = int]’ at /usr/include/c++/15.2.1/bits/alloc_traits.h:614:28,
    inlined from ‘std::_Vector_base<_Tp, _Alloc>::pointer std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp = int; _Alloc = std::allocator<int>]’ at /usr/include/c++/15.2.1/bits/stl_vector.h:387:33,
    inlined from ‘void std::_Vector_base<_Tp, _Alloc>::_M_create_storage(std::size_t) [with _Tp = int; _Alloc = std::allocator<int>]’ at /usr/include/c++/15.2.1/bits/stl_vector.h:405:44,
    inlined from ‘std::_Vector_base<_Tp, _Alloc>::_Vector_base(std::size_t, const allocator_type&) [with _Tp = int; _Alloc = std::allocator<int>]’ at /usr/include/c++/15.2.1/bits/stl_vector.h:341:26,
    inlined from ‘std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>]’ at /usr/include/c++/15.2.1/bits/stl_vector.h:633:61,
    inlined from ‘static void Assimp::X3DGeoHelper::coordIdx_str2lines_arr(const std::vector<int>&, std::vector<aiFace>&)’ at /opt/mlibrary/cadmesh/external/assimp/code/AssetLib/X3D/X3DGeoHelper.cpp:192:42:
/usr/include/c++/15.2.1/bits/new_allocator.h:151:73: note: at offset -4 into object of size [4, 9223372036854775804] allocated by ‘operator new’
  151 |         return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
      |                                                                         ^
cc1plus: all warnings being treated as errors
make[5]: *** [code/CMakeFiles/assimp.dir/build.make:2571: code/CMakeFiles/assimp.dir/AssetLib/X3D/X3DGeoHelper.cpp.o] Error 1
make[5]: *** Waiting for unfinished jobs....
make[4]: *** [CMakeFiles/Makefile2:184: code/CMakeFiles/assimp.dir/all] Error 2
make[3]: *** [Makefile:136: all] Error 2
make[2]: *** [CMakeFiles/assimp_external.dir/build.make:86: assimp_external-prefix/src/assimp_external-stamp/assimp_external-build] Error 2
make[1]: *** [CMakeFiles/Makefile2:147: CMakeFiles/assimp_external.dir/all] Error 2
make: *** [Makefile:156: all] Error 2