Segfault when setting References via the default setter

[Windfisch]

Commit 01606fa introduced the following bug for me:
My class has a Ref<Mesh> property with the default setter/getter functions. Since aforementioned commit, my Game instantly segfaults with the stack trace attached below.
Reverting 01606fa makes everything work again.

Thread 1 "godot.x11.tools" received signal SIGSEGV, Segmentation fault.
0x000000000175110f in godot_method_bind_ptrcall (p_method_bind=0x0, p_instance=0x6dfaa50, p_args=0x7fffffffd6c0, p_ret=0x7fffffffd6bf)
    at modules/gdnative/gdnative/gdnative.cpp:69
69              mb->ptrcall(o, p_args, p_ret);
(gdb) bt
#0  0x000000000175110f in godot_method_bind_ptrcall (p_method_bind=0x0, p_instance=0x6dfaa50, p_args=0x7fffffffd6c0, p_ret=0x7fffffffd6bf)
    at modules/gdnative/gdnative/gdnative.cpp:69
#1  0x00007fffec7c610d in godot::___godot_icall_bool (inst=<optimized out>, mb=<optimized out>) at include/gen/__icalls.hpp:5403
#2  godot::Reference::reference (this=<optimized out>) at src/gen/Reference.cpp:34
#3  0x00007fffec7ad2b8 in godot::Ref<godot::Mesh>::ref (p_from=..., this=0x7fffffffd6e0) at godot-cpp/include/core/Ref.hpp:175
#4  godot::Ref<godot::Mesh>::Ref (p_variant=..., this=0x7fffffffd6e0) at godot-cpp/include/core/Ref.hpp:168
#5  godot::_ArgCast<godot::Ref<godot::Mesh> >::_arg_cast (a=...) at godot-cpp/include/core/Godot.hpp:78
#6  godot::_PropertyDefaultSetFunc<godot::Visualizer, godot::Ref<godot::Mesh> >::_wrapped_setter (object=<optimized out>, method_data=0xc133e40, 
    user_data=0xc4f0770, value=<optimized out>) at godot-cpp/include/core/Godot.hpp:290
#7  0x0000000001757490 in NativeScriptInstance::set (this=0xc35d840, p_name=..., p_value=...) at modules/gdnative/nativescript/nativescript.cpp:571
#8  0x000000000354d4ba in Object::set (this=0xc55e480, p_name=..., p_value=..., r_valid=0x7fffffffda68) at core/object.cpp:413
#9  0x0000000002faa253 in SceneState::instance (this=0xc387a40, p_edit_state=SceneState::GEN_EDIT_STATE_DISABLED)
    at scene/resources/packed_scene.cpp:254
#10 0x0000000002fb4b0f in PackedScene::instance (this=0xc52e570, p_edit_state=PackedScene::GEN_EDIT_STATE_DISABLED)
    at scene/resources/packed_scene.cpp:1699
#11 0x0000000001335afd in Main::start () at main/main.cpp:1736
#12 0x00000000012fa8ff in main (argc=1, argv=0x7fffffffe788) at platform/x11/godot_x11.cpp:54

(The line numbers are relative to Godot f75b9e62468ba65753f2ce49c02f1a129c08b717, btw)