### 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 < index_sets.size(); i++) {
		RBSet<int> iset = index_sets[i];
		while (iset.size() > 1) {
			
			for (const int &E : iset) {
				int set_idx = E;
				String scene_name = r_filenames[set_idx];
				String full_path = p_full_paths[set_idx];
				
				scene_name = scene_name.get_basename();
				if (full_path.begins_with("res:")) {
					full_path = full_path.substr(6);
				}
				full_path = full_path.get_basename();
				
				scene_name = scene_name.trim_suffix("/");
				full_path = full_path.trim_suffix("/");
				int scene_name_size = scene_name.size();
				int full_path_size = full_path.size();
				int difference = full_path_size - scene_name_size;
				
				
				
				
				if (difference > 0) {
					String parent = full_path.substr(0, difference);
					int slash_idx = parent.rfind("/");
					slash_idx = parent.rfind("/", slash_idx - 1);