### 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)

_send_window_event(windows[window_mouseover_id], WINDOW_EVENT_MOUSE_EXIT);
					}
					if (over_id != INVALID_WINDOW_ID && windows.has(over_id)) {
						_send_window_event(windows[over_id], WINDOW_EVENT_MOUSE_ENTER);
					}
				}
				CursorShape c = cursor_shape;
				cursor_shape = CURSOR_MAX;
				cursor_set_shape(c);
				window_mouseover_id = over_id;
				
				track_mouse_leave_event(hWnd);
			}
			
			if (!windows[window_id].window_has_focus && mouse_mode == MOUSE_MODE_CAPTURED) {
				break;
			}
			DisplayServer::WindowID receiving_window_id = _get_focused_window_or_popup();
			if (receiving_window_id == INVALID_WINDOW_ID) {
				receiving_window_id = window_id;
			}
			Ref<InputEventMouseMotion> mm;
			mm.instantiate();
			mm->set_window_id(receiving_window_id);
			mm->set_ctrl_pressed((wParam & MK_CONTROL) != 0);
			mm->set_shift_pressed((wParam & MK_SHIFT) != 0);
			mm->set_alt_pressed(alt_mem);
			if ((tablet_get_current_driver() == "wintab") && wintab_available && windows[window_id].wtctx) {
				
				if (windows[window_id].last_pressure_update < 10) {