### 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
if (InspectorDock::get_inspector_singleton()) {
		InspectorDock::get_inspector_singleton()->update_tree();
	}
}
void EditorNode::_editor_select_next() {
	int editor = _get_current_main_editor();
	do {
		if (editor == editor_table.size() - 1) {
			editor = 0;
		} else {
			editor++;
		}
	} while (!main_editor_buttons[editor]->is_visible());
	editor_select(editor);
}
void EditorNode::_open_command_palette() {
	command_palette->open_popup();
}
void EditorNode::_editor_select_prev() {
	int editor = _get_current_main_editor();
	do {
		if (editor == 0) {
			editor = editor_table.size() - 1;
		} else {
			editor--;
		}
	} while (!main_editor_buttons[editor]->is_visible());
	editor_select(editor);
}
Error EditorNode::load_resource(const String &p_resource, bool p_ignore_broken_deps) {