### 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 < DOCK_SLOT_MAX; i++) {
		if (dock_slot[i]->get_tab_count() == 0 && dock_slot[i]->is_visible()) {
			dock_slot[i]->hide();
		}
		if (dock_slot[i]->get_tab_count() > 0 && !dock_slot[i]->is_visible()) {
			dock_slot[i]->show();
		}
	}
	for (int i = 0; i < vsplits.size(); i++) {
		bool in_use = dock_slot[i * 2 + 0]->get_tab_count() || dock_slot[i * 2 + 1]->get_tab_count();
		if (in_use) {
			vsplits[i]->show();
		} else {
			vsplits[i]->hide();
		}
	}
	if (right_l_vsplit->is_visible() || right_r_vsplit->is_visible()) {
		right_hsplit->show();
	} else {
		right_hsplit->hide();
	}
}
void EditorNode::_dock_select_input(const Ref<InputEvent> &p_input) {