[v4] shell32: fix two bugs in IQueryAssocations

[Marvin]

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
https://testbot.winehq.org/JobDetails.pl?Key=20568

Your paranoid android.


=== w2003std (32 bit assoc) ===
assoc.c:122: Test failed: GetString returned 0x80070002, expected 0x0
assoc.c:174: Test failed: 
assoc.c:122: Test failed: GetString returned 0x80070002, expected 0x0
assoc.c:178: Test failed: 
assoc.c:122: Test failed: GetString returned 0x80070002, expected 0x80070483
assoc.c:183: Test failed: 
assoc.c:122: Test failed: GetString returned 0x80070002, expected 0x80070483
assoc.c:184: Test failed: 
assoc.c:122: Test failed: GetString returned 0x80070002, expected 0x80070483
assoc.c:185: Test failed: