### Godot version

4.0.2.stable

### System information

Fedora 37, GeForce RTX 4090 (NVIDIA 530.41.03)

### Issue description

Physical Keycode and Key Label options appear grayed out in the input editor when editing an existing key, even though I should logically be able to change it:

![image](https://github.com/godotengine/godot/assets/180032/54d4c3a5-4da5-4448-b42a-42f0c6870cc2)

If I set the key to another key then change it back, then the **Physical Keycode** and **Key Label** options are no longer grayed out.

cc @bruvzg

### Steps to reproduce

- Open the Project Settings > Input Map tab.
- Create an action, with an associated key. Save it.
- Click the edit button next to the key, and try to change the type without touching the actual key's value.
- Change the key's value back and forth and try to change the type using the dropdown again.

### Minimal reproduction project

N/A
if (p_event.is_valid()) {
		event = p_event;
		original_event = p_original_event;
		
		
		const Ref<InputEvent> listener_event = event_listener->get_event();
		if (listener_event.is_valid() && !listener_event->is_match(p_event)) {
			event_listener->clear_event();
		}
		
		event_as_text->set_text(EventListenerLineEdit::get_event_text(event, true));
		Ref<InputEventKey> k = p_event;
		Ref<InputEventMouseButton> mb = p_event;
		Ref<InputEventJoypadButton> joyb = p_event;
		Ref<InputEventJoypadMotion> joym = p_event;
		Ref<InputEventWithModifiers> mod = p_event;
		
		bool show_mods = false;
		bool show_device = false;
		bool show_key = false;
		if (mod.is_valid()) {