advapi32: Fix GetSecurityInfo with NULL descriptor

[testbot at testbot.winehq.org]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
http://testbot.winehq.org/JobDetails.pl?Key=2467

Your paranoid android.


=== WNT4WSSP6 (32 bit security) ===
No test summary line found