[PATCH] msctf/tests: Fix a crash on unsupported interface

[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=21569

Your paranoid android.


=== w864 (32 bit inputprocessor) ===
inputprocessor.c:787: Test failed: Deactivation came unexpectedly

=== w1064 (64 bit inputprocessor) ===
inputprocessor.c:787: Test failed: Deactivation came unexpectedly