Problem with ffmpeg-free

[Christoph Pleger]

Hello,

> +
> +    if (!c) {
> +        av_log(c, AV_LOG_ERROR, "swScaler: SwsContext invalid\n");
> +    }

The problem was not solved. I expected that, as the four lines do not really 
change anything but add a debugging message. As that message appeared in my 
standard output, we can now be sure that c being NULL causes the segmentation 
fault.

Regards
  Christoph