msacm32: Avoid attempts to convert data when available output is negative in acmStreamConvert

[Bruno Jesus]

On Mon, Nov 23, 2015 at 10:28 PM, Andrew Eikum <aeikum at codeweavers.com> wrote:
> This doesn't seem right to me. The test succeeds even without your
> changes to msacm32/stream.c because cbDstLength != cbPreparedDstLength
> in acmStreamConvert. I tried moving cbDstLength=-4 before
> PrepareHeader, and both PrepareHeader and Convert succeed on my Win7
> VM.
>
> Can you look further into this?

Hi, Andrew. Thanks for the review, you are right! I thought my tests
were good but it turns out they didn't really test what I was
expecting. I'm trying to understand this better, I will probably
resend the tests alone next time.

Best wishes,
Bruno