### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

k->set_window_id(ke.window_id);
					k->set_shift_pressed(ke.shift);
					k->set_alt_pressed(ke.alt);
					k->set_ctrl_pressed(ke.control);
					k->set_meta_pressed(ke.meta);
					k->set_pressed(true);
					k->set_keycode(keycode);
					k->set_physical_keycode(physical_keycode);
					k->set_key_label(key_label);
					k->set_unicode(fix_unicode(unicode));
					if (k->get_unicode() && gr_mem) {
						k->set_alt_pressed(false);
						k->set_ctrl_pressed(false);
					}
					Input::get_singleton()->parse_input_event(k);
				} else {
					
				}
			} break;
			case WM_KEYUP:
			case WM_KEYDOWN: {
				Ref<InputEventKey> k;
				k.instantiate();
				k->set_window_id(ke.window_id);
				k->set_shift_pressed(ke.shift);
				k->set_alt_pressed(ke.alt);
				k->set_ctrl_pressed(ke.control);
				k->set_meta_pressed(ke.meta);
				k->set_pressed(ke.uMsg == WM_KEYDOWN);
				Key keycode = KeyMappingWindows::get_keysym(ke.wParam);