### 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)

old_y = mm->get_position().y;
					if (windows[window_id].window_has_focus || window_get_active_popup() == window_id) {
						Input::get_singleton()->parse_input_event(mm);
					}
				}
				return 0;
			}
		} break;
		case WM_POINTERENTER: {
			if (mouse_mode == MOUSE_MODE_CAPTURED && use_raw_input) {
				break;
			}
			if ((tablet_get_current_driver() != "winink") || !winink_available) {
				break;
			}
			uint32_t pointer_id = LOWORD(wParam);
			POINTER_INPUT_TYPE pointer_type = PT_POINTER;
			if (!win8p_GetPointerType(pointer_id, &pointer_type)) {
				break;
			}
			if (pointer_type != PT_PEN) {
				break;
			}
			windows[window_id].block_mm = true;
			return 0;
		} break;
		case WM_POINTERLEAVE: {
			windows[window_id].block_mm = false;
			return 0;
		} break;