Contents of `mixwfe` is copied into `wfe` and `mixwfe` is freed by `CoTaskMemFree`. But then `mixwfe` is used again. This patch uses the values from `wfe`.
[This is a testbot run with this patch](https://testbot.winehq.org/JobDetails.pl?Key=160647)
[ASan details found by gitlab-CI](https://gitlab.winehq.org/bernhardu/wine/-/jobs/205270#L530)