[PATCH] dwrite: use correct variable (Coverity)

[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=8996

Your paranoid android.


=== wvistau64 (32 bit font) ===
font.c:961: Test failed: got 0x80070057

=== w2008s64 (32 bit font) ===
font.c:961: Test failed: got 0x80070057

=== w7u (32 bit font) ===
font.c:961: Test failed: got 0x80070057

=== w8 (32 bit font) ===
font.c:961: Test failed: got 0x80070057

=== wvistau64 (64 bit font) ===
font.c:961: Test failed: got 0x80070057

=== w2008s64 (64 bit font) ===
font.c:961: Test failed: got 0x80070057