### 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
Dictionary state;
	state["main_tab"] = _get_current_main_editor();
	state["scene_tree_offset"] = SceneTreeDock::get_singleton()->get_tree_editor()->get_scene_tree()->get_vscroll_bar()->get_value();
	state["property_edit_offset"] = InspectorDock::get_inspector_singleton()->get_scroll_offset();
	state["node_filter"] = SceneTreeDock::get_singleton()->get_filter();
	return state;
}
void EditorNode::_set_main_scene_state(Dictionary p_state, Node *p_for_scene) {
	if (get_edited_scene() != p_for_scene && p_for_scene != nullptr) {
		return; 
	}
	changing_scene = false;
	int current_tab = -1;
	for (int i = 0; i < editor_table.size(); i++) {
		if (editor_plugin_screen == editor_table[i]) {
			current_tab = i;
			break;
		}
	}
	if (p_state.has("editor_index")) {
		int index = p_state["editor_index"];
		if (current_tab < 2) { 
			if (index < 2 || !get_edited_scene()) {
				editor_select(index);