Must call Py_INCREF on bpy_mesh_ptr

[SausageTaste]

io_scene_dalbaragi/cpp/b3dsung.cpp

Line 469 in 768b839

auto bpy_mesh = ::PythonObject{bpy_mesh_ptr, true};

The bpy_mesh_ptr is borrowed reference, and it may be destroyed while std::async is using it.
Calling Py_INCREF(bpy_mesh_ptr) before the line will fix the problem.

On the other hand, Py_DECREF is not necessary.
Note the second arguemnt true in the ::PythonObject constructor.

[SausageTaste]

I was blind that I didn't see it was there alerady.