gdiplus: Only clip strings if rectangle width and height are positive.

[Vincent Povirk]

>>      if (!(format_flags & StringFormatFlagsNoClip) &&
>> -        scaled_rect.Width != 1 << 23 && scaled_rect.Height != 1 << 23)
>> +        scaled_rect.Width != 1 << 23 && scaled_rect.Height != 1 << 23 &&
>> +        rect->Width > 0.0 && rect->Height > 0.0)
>>      {
>>          /* FIXME: If only the width or only the height is 0, we should probably still clip */
>>          rgn = CreatePolygonRgn(corners, 4, ALTERNATE);
>
> Probably FIXME should be removed then.

I dunno, I still haven't tested that case.