arsd png bug

[Adam D. Ruppe via Digitalmars-d-learn]

On Monday, 20 June 2016 at 21:39:45 UTC, Joerg Joergonson wrote:
> adding
> 	if (i >= previousLine.length) break;
>
> prevents some crashes and seems to work.

So previousLine should be either the right length or null, so I 
put in one test.

Can you try it on your test image?

BTW I do a few unnecessary duplications in here too. I think. But 
there's surely some potential for more memory/performance 
improvements here.