### Godot version

v4.0.stable.official [92bee43ad]

### System information

Linux - v4.0.stable.official [92bee43ad]

### Issue description

It gives you the possibility of removing unexisting key/value pairs from a dictionary.

### Steps to reproduce

![image](https://github.com/godotengine/godot/assets/69520693/35beadbe-bfdd-4176-9b26-222bbf69cafa)
![image](https://github.com/godotengine/godot/assets/69520693/7ed647e0-a2af-4e58-9f00-f77b7bc7bb02)
![image](https://github.com/godotengine/godot/assets/69520693/f08bf824-8408-45eb-bb84-f1dc7e19e392)


### Minimal reproduction project

N/A
if (i == amount) {
				PanelContainer *pc = memnew(PanelContainer);
				property_vbox->add_child(pc);
				pc->add_theme_style_override(SNAME("panel"), get_theme_stylebox(SNAME("DictionaryAddItem"), SNAME("EditorStyles")));
				add_vbox = memnew(VBoxContainer);
				pc->add_child(add_vbox);
			}
			prop->set_object_and_property(object.ptr(), prop_name);
			int change_index = 0;
			if (i < amount) {
				String cs = key.get_construct_string();
				prop->set_label(key.get_construct_string());
				prop->set_tooltip_text(cs);
				change_index = i + offset;
			} else if (i == amount) {
				prop->set_label(TTR("New Key:"));
				change_index = -1;
			} else if (i == amount + 1) {
				prop->set_label(TTR("New Value:"));
				change_index = -2;
			}
			prop->set_selectable(false);
			prop->connect("property_changed", callable_mp(this, &EditorPropertyDictionary::_property_changed));
			prop->connect("object_id_selected", callable_mp(this, &EditorPropertyDictionary::_object_id_selected));
			HBoxContainer *hbox = memnew(HBoxContainer);
			if (add_vbox) {
				add_vbox->add_child(hbox);
			} else {
				property_vbox->add_child(hbox);
			}