[Bug 36597] valgrind shows several definite leaks in user32/tests/msg.c

https://bugs.winehq.org/show_bug.cgi?id=36597

--- Comment #4 from Austin English  ---
(In reply to Sebastian Lackner from comment #3)
> Created attachment 48864 [details]
> user32/tests: Add a missing call to ReleaseActCtx().
>
> Ah, you're right. Didn't notice they made the same mistake as in the other
> tests, sorry :/ Does this one finally fix it?

Works, thanks.