Fix AVX2 itx crash on 64-bit Windows

Accidentally broken in eb01bdb9.
12 jobs for master in 4 minutes and 55 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #244056
amd64 debian
build-debian

00:00:36

passed #244060
debian aarch64
build-debian-aarch64

00:01:29

passed #244061
debian aarch64
build-debian-aarch64-clang-5

00:01:04

passed #244057
amd64 debian
build-debian-static

00:00:32

passed #244063
debian aarch64
build-debian-werror

00:00:34

passed #244062
macos
build-macos

00:00:27

passed #244058
win32
build-win32

00:00:28

passed #244059
win64
build-win64

00:00:37

 
  Test
passed #244064
amd64 debian
test-debian

00:00:47

passed #244065
amd64 debian
test-debian-asan

00:02:00

passed #244066
amd64 debian
test-debian-msan

00:01:02

passed #244067
amd64 debian
test-debian-ubsan

00:01:22