[PATCH] Fix a crash in dlls/shell32/tests/shlfolder.c

[Sami Aario]

dlls/shell32/tests/shlfolder.c does not check the return value of
a SHGetDesktopFolder call, and subsequently crashes when a
call is made using an uninitialized IDesktopFolder interface. Fix
this.

Changelog:
    Fix a crash in dlls/shell32/tests/shlfolder.c