### 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)

Size2 decor = window_get_size_with_decorations(window_id) - window_get_size(window_id);
				MINMAXINFO *min_max_info = (MINMAXINFO *)lParam;
				if (windows[window_id].min_size != Size2()) {
					min_max_info->ptMinTrackSize.x = windows[window_id].min_size.x + decor.x;
					min_max_info->ptMinTrackSize.y = windows[window_id].min_size.y + decor.y;
				}
				if (windows[window_id].max_size != Size2()) {
					min_max_info->ptMaxTrackSize.x = windows[window_id].max_size.x + decor.x;
					min_max_info->ptMaxTrackSize.y = windows[window_id].max_size.y + decor.y;
				}
				return 0;
			}
		} break;
		case WM_ERASEBKGND: {
			Color early_color;
			if (!_get_window_early_clear_override(early_color)) {
				break;
			}
			bool must_recreate_brush = !window_bkg_brush || window_bkg_brush_color != early_color.to_argb32();
			if (must_recreate_brush) {
				if (window_bkg_brush) {
					DeleteObject(window_bkg_brush);
				}
				window_bkg_brush = CreateSolidBrush(RGB(early_color.get_r8(), early_color.get_g8(), early_color.get_b8()));
			}
			HDC hdc = (HDC)wParam;
			RECT rect = {};
			if (GetUpdateRect(hWnd, &rect, true)) {
				FillRect(hdc, &rect, window_bkg_brush);