### 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
for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == p_path) {
			return true;
		}
	}
	return false;
}
void EditorNode::fix_dependencies(const String &p_for_file) {
	dependency_fixer->edit(p_for_file);
}
int EditorNode::new_scene() {
	int idx = editor_data.add_edited_scene(-1);
	
	if (editor_data.get_edited_scene_count() > 1) {
		for (int i = 0; i < editor_data.get_edited_scene_count() - 1; i++) {
			bool unsaved = EditorUndoRedoManager::get_singleton()->is_history_unsaved(editor_data.get_scene_history_id(i));
			if (!unsaved && editor_data.get_scene_path(i).is_empty() && editor_data.get_edited_scene_root(i) == nullptr) {
				editor_data.remove_scene(i);
				idx--;
			}
		}
	}
	idx = MAX(idx, 0);
	_scene_tab_changed(idx);
	editor_data.clear_editor_states();
	_update_scene_tabs();
	return idx;
}
Error EditorNode::load_scene(const String &p_scene, bool p_ignore_broken_deps, bool p_set_inherited, bool p_clear_errors, bool p_force_open_imported, bool p_silent_change_tab) {