MSVC 2019 complains that the code at line 1744
(`GetMonitorInfo(window->monitor->win32.handle, &mi);`) can potentially
dereference a null pointer. The compiler is wrong in this case (it has
not spotted that `monitor` and `window->monitor` must be equal), but
I think it makes sense for our non-NULL test to be on the variable we
actually use rather than the one it was set from.

Related to #1491.

(cherry picked from commit 1d6215726807e73fd21da9a4a09c28aab3111879)