mapi32: Write-strings warnings fix

[Andrew Talbot]

Hans Leidekker wrote:
> 
> Don't be sorry. I like your persistence.

And I appreciate your kindness, thank you.

> I see what you mean now, yes address doesn't have to be initialised,
> there's no way it could be used uninitialised in this code.
> 
>  -Hans

I shall let the dust settle, then probably put in another patch to remove
the superfluous initialisation.

Thanks,

-- Andy.