pdh: check for NULL pointer reference

[Hans Leidekker]

On Monday 22 October 2007 11:30:10 Jeff Latimer wrote:

> This function has specific XP behaviour which I have tested but I have 
> not been able to verify that Win2k etc works the same.  Any comment welcome.

I don't think we want to emulate the broken XP behaviour of requiring a
buffer, even when querying the buffer size. Apps written to comply with
this behaviour should work on the current implementation. And MSDN mentions
only XP, which implies that it has been fixed in Win2k3 and up.

 -Hans