### Godot version

4.0.3.stable

### System information

Windows 10/11

### Issue description

I want the player's cursor to change when highlighting pickable Area2Ds; to do this, I have the areas modify the `mouse_default_cursor_shape` property on an external Control when the mouse enters or exits. If another Control appears in front of the Area2D while the mouse is over it, there is a chance that the project will crash.

Nothing prints to the IDE's output on this crash. If running the editor with console, then
```
ERROR: Condition "slot >= slot_max" is true. Returning: nullptr
   at: get_instance (./core/object/object.h:972)
```
will sometimes appear alongside the crash. If it appears, it always appears twice.

When I run a debug build of the editor through WinDbg, WinDbg will catch the following exception:
```
(3b58.2aac): Access violation - code c0000005 (!!! second chance !!!)
godot_windows_editor_x86_64!ObjectDB::get_instance [inlined in godot_windows_editor_x86_64!Viewport::_cleanup_mouseover_colliders+0x6f]:
00007ff6`ac254a1f 488b5310        mov     rdx,qword ptr [rbx+10h] ds:cccccccc`c31c419b=????????????????
```
When using this method, the exception is not random; it always occurs on the first attempt.

### Steps to reproduce

- Open the minimal reproduction project in the editor.
- Run the project.
- Click on the Area2D (you'll want visible collision shapes on).
- A full-screen button will pop up. If the game does not crash at this point, clicking the button will hide it so you can try again. It should crash within a few seconds of mashing.

### Minimal reproduction project

[Crash Test.zip](https://github.com/godotengine/godot/files/12027772/Crash.Test.zip)

CollisionObject2D *a = Object::cast_to<CollisionObject2D>(p_a.collider);
							CollisionObject2D *b = Object::cast_to<CollisionObject2D>(p_b.collider);
							if (!a || !b) {
								return false;
							}
							int za = a->get_effective_z_index();
							int zb = b->get_effective_z_index();
							if (za != zb) {
								return zb < za;
							}
							return a->is_greater_than(b);
						}
					};
					SortArray<PhysicsDirectSpaceState2D::ShapeResult, ComparatorCollisionObjects> sorter;
					sorter.sort(res, rc);
				}
				for (int i = 0; i < rc; i++) {
					if (res[i].collider_id.is_valid() && res[i].collider) {
						CollisionObject2D *co = Object::cast_to<CollisionObject2D>(res[i].collider);
						if (co && co->can_process()) {
							bool send_event = true;
							if (is_mouse) {
								HashMap<ObjectID, uint64_t>::Iterator F = physics_2d_mouseover.find(res[i].collider_id);
								if (!F) {
									physics_2d_mouseover.insert(res[i].collider_id, frame);
									co->_mouse_enter();
								} else {
									F->value = frame;