Merge pull request #2895 from tomponline/tp-2019-03-05/minor-fix

conf: Fixes uninitialised variable.

> @brauner clang is failing but gcc passes, would it be OK to initialise this to 0?

He, unfortunately not. :)
What would happen now is that you'd close `stdin` on a standard system. What you'd want is `= -EBADF`. :)