fix segfault in EmbreeScene.__dealloc__, due to use-after-free of EmbreeDevice

[pbsds]

pytest + gdb backtrace output, with embree v2.17.7 compiled with -DCMAKE_BUILD_TYPE=RelWithDebInfo:

============================= test session starts ==============================
platform linux -- Python 3.12.9, pytest-8.3.5, pluggy-1.5.0 -- /nix/store/fqm9bqqlmaqqr02qbalm1bazp810qfiw-python3-3.12.9/bin/python3.12
cachedir: .pytest_cache
rootdir: /build/source
configfile: pyproject.toml
collected 13 items

tests/test_intersection.py::TestPyEmbree::test_pyembree_should_be_able_to_create_a_device_if_not_provided PASSED [  7%]
tests/test_intersection.py::TestPyEmbree::test_pyembree_should_be_able_to_create_a_scene PASSED [ 15%]
tests/test_intersection.py::TestPyEmbree::test_pyembree_should_be_able_to_create_several_scenes PASSED [ 23%]
tests/test_intersection.py::TestPyEmbree::test_pyembree_should_be_able_to_display_embree_version PASSED [ 30%]
tests/test_intersection.py::TestIntersectionTriangles::test_intersect PASSED [ 38%]
Thread 1 "python3.12" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
#0  0x0000000000000000 in ?? ()
#1  0x00007fffb1e7e76f in embree::APIBuffer<embree::Vec3fa>::free (this=0x8cb7b0) at /build/source/kernels/common/buffer.h:212
#2  embree::APIBuffer<embree::Vec3fa>::~APIBuffer (this=0x8cb7b0, __in_chrg=<optimized out>) at /build/source/kernels/common/buffer.h:137
#3  std::__new_allocator<embree::APIBuffer<embree::Vec3fa> >::destroy<embree::APIBuffer<embree::Vec3fa> > (this=0x9357a8, __p=0x8cb7b0) at /nix/store/qs54xir5n4vhhbi22aydbkvyyq4v8p0l-gcc-14.2.1.20250322/include/c++/14.2.1.20250322/bits/new_allocator.h:198
#4  embree::vector_t<embree::APIBuffer<embree::Vec3fa>, std::allocator<embree::APIBuffer<embree::Vec3fa> > >::clear (this=0x9357a8) at /build/source/kernels/common/../../common/sys/vector.h:148
        i = 0
#5  embree::vector_t<embree::APIBuffer<embree::Vec3fa>, std::allocator<embree::APIBuffer<embree::Vec3fa> > >::~vector_t (this=0x9357a8, __in_chrg=<optimized out>) at /build/source/kernels/common/../../common/sys/vector.h:42
#6  embree::TriangleMesh::~TriangleMesh (this=0x9356b0, __in_chrg=<optimized out>) at /build/source/kernels/common/scene_triangle_mesh.h:25
#7  embree::avx::TriangleMeshISA::~TriangleMeshISA (this=0x9356b0, __in_chrg=<optimized out>) at /build/source/kernels/common/scene_triangle_mesh.h:220
#8  embree::avx::TriangleMeshISA::~TriangleMeshISA (this=0x9356b0, __in_chrg=<optimized out>) at /build/source/kernels/common/scene_triangle_mesh.h:220
#9  0x00007fffb174744f in embree::Scene::~Scene (this=0xb45dc0, __in_chrg=<optimized out>) at /build/source/kernels/common/scene.cpp:594
        i = 0
        i = <optimized out>
#10 0x00007fffb17475e9 in embree::Scene::~Scene (this=0xb45dc0, __in_chrg=<optimized out>) at /build/source/kernels/common/scene.cpp:599
        i = <optimized out>
#11 0x00007ffff3565de8 in __pyx_pf_8pyembree_12rtcore_scene_11EmbreeScene_4__dealloc__ (__pyx_v_self=0x7fffb3055e00) at pyembree/rtcore_scene.cpp:3957

Which indicates the segfault happens in

https://github.com/RenderKit/embree/blob/8b2ad69f899ca0710f94d10303a2f02d7426faaf/kernels/common/buffer.h#L212