### 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)

ERR_READ_THREAD_GUARD_V(0);
	return positional_shadow_atlas_size;
}
void Viewport::set_positional_shadow_atlas_16_bits(bool p_16_bits) {
	ERR_MAIN_THREAD_GUARD;
	if (positional_shadow_atlas_16_bits == p_16_bits) {
		return;
	}
	positional_shadow_atlas_16_bits = p_16_bits;
	RS::get_singleton()->viewport_set_positional_shadow_atlas_size(viewport, positional_shadow_atlas_size, positional_shadow_atlas_16_bits);
}
bool Viewport::get_positional_shadow_atlas_16_bits() const {
	ERR_READ_THREAD_GUARD_V(false);
	return positional_shadow_atlas_16_bits;
}
void Viewport::set_positional_shadow_atlas_quadrant_subdiv(int p_quadrant, PositionalShadowAtlasQuadrantSubdiv p_subdiv) {
	ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_quadrant, 4);
	ERR_FAIL_INDEX(p_subdiv, SHADOW_ATLAS_QUADRANT_SUBDIV_MAX);
	if (positional_shadow_atlas_quadrant_subdiv[p_quadrant] == p_subdiv) {
		return;
	}
	positional_shadow_atlas_quadrant_subdiv[p_quadrant] = p_subdiv;
	static const int subdiv[SHADOW_ATLAS_QUADRANT_SUBDIV_MAX] = { 0, 1, 4, 16, 64, 256, 1024 };
	RS::get_singleton()->viewport_set_positional_shadow_atlas_quadrant_subdivision(viewport, p_quadrant, subdiv[p_subdiv]);
}
Viewport::PositionalShadowAtlasQuadrantSubdiv Viewport::get_positional_shadow_atlas_quadrant_subdiv(int p_quadrant) const {