### 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)

encode_uint32(40, &icon_bmp[0]);
	encode_uint32(w, &icon_bmp[4]);
	encode_uint32(h * 2, &icon_bmp[8]);
	encode_uint16(1, &icon_bmp[12]);
	encode_uint16(32, &icon_bmp[14]);
	encode_uint32(BI_RGB, &icon_bmp[16]);
	encode_uint32(w * h * 4, &icon_bmp[20]);
	encode_uint32(0, &icon_bmp[24]);
	encode_uint32(0, &icon_bmp[28]);
	encode_uint32(0, &icon_bmp[32]);
	encode_uint32(0, &icon_bmp[36]);
	uint8_t *wr = &icon_bmp[40];
	const uint8_t *r = icon->get_data().ptr();
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			const uint8_t *rpx = &r[((h - i - 1) * w + j) * 4];
			uint8_t *wpx = &wr[(i * w + j) * 4];
			wpx[0] = rpx[2];
			wpx[1] = rpx[1];
			wpx[2] = rpx[0];
			wpx[3] = rpx[3];
		}
	}
	HICON hicon = CreateIconFromResource(icon_bmp, icon_len, TRUE, 0x00030000);
	
	SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_SMALL, (LPARAM)hicon);
	
	SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_BIG, (LPARAM)hicon);
}
void DisplayServerWindows::window_set_vsync_mode(DisplayServer::VSyncMode p_vsync_mode, WindowID p_window) {