### 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
}
				atidx = k;
				break;
			}
			if (atidx == -1) {
				
				for (WindowWrapper *wrapper : floating_docks) {
					if (wrapper->get_meta("dock_name") == name) {
						if (restore_window_on_load && floating_docks_dump.has(name)) {
							_restore_floating_dock(floating_docks_dump[name], wrapper, i);
							return;
						} else {
							_dock_floating_close_request(wrapper);
							atidx = wrapper->get_meta("dock_index");
						}
					}
				}
				
				continue;
			}
			if (atidx == i) {
				dock_slot[i]->move_child(node, 0);
			} else if (atidx != -1) {
				dock_slot[atidx]->remove_child(node);
				if (dock_slot[atidx]->get_tab_count() == 0) {
					dock_slot[atidx]->hide();
				}
				dock_slot[i]->add_child(node);
				dock_slot[i]->move_child(node, 0);
				dock_slot[i]->set_tab_title(0, TTRGET(node->get_name()));