### Godot version

v4.2.dev.custom_build [0c2144da9]

### System information

Debian Linux X11 Xfce

### Issue description

Prerequisite: Be in Single Window Mode in the Editor
The Filesystem Dock is unusable when it is floating, which is not expected.
It appears garbled in the top-left corner:
![image](https://github.com/godotengine/godot/assets/6299227/109f7922-97de-44c3-814a-ca7f970e0602)

The following errors are shown:
```
  editor/window_wrapper.cpp:220 - Condition "!is_window_available()" is true.
  editor/window_wrapper.cpp:202 - Condition "!get_window_enabled()" is true. Returning: Rect2i()
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
```

bisecting lead to #62378
possibly related to #44439

### Steps to reproduce

1. Start a project in the Editor
2. Switch to Single Window Mode in the Editor and reload (if necessary)
3. Make the Filesystem Dock floating

### Minimal reproduction project

Editor issue
file_menu->set_item_disabled(file_menu->get_item_index(FILE_OPEN_PREV), previous_scenes.is_empty());
	_update_undo_redo_allowed();
}
void EditorNode::_update_file_menu_closed() {
	file_menu->set_item_disabled(file_menu->get_item_index(FILE_OPEN_PREV), false);
}
VBoxContainer *EditorNode::get_main_screen_control() {
	return main_screen_vbox;
}
void EditorNode::editor_select(int p_which) {
	static bool selecting = false;
	if (selecting || changing_scene) {
		return;
	}
	ERR_FAIL_INDEX(p_which, editor_table.size());
	if (!main_editor_buttons[p_which]->is_visible()) { 
		return;
	}
	selecting = true;
	for (int i = 0; i < main_editor_buttons.size(); i++) {
		main_editor_buttons[i]->set_pressed(i == p_which);
	}
	selecting = false;
	EditorPlugin *new_editor = editor_table[p_which];
	ERR_FAIL_COND(!new_editor);
	if (editor_plugin_screen == new_editor) {
		return;