Update zloop.c

[Crossverse]

Code mistake

[c-rack]

Thanks! ❤️

For your next pull request, could you please use our "Problem / Solution" pattern?

Before sending a pull request make sure each commit solves one clear, minimal, plausible problem. Further each commit should have the following format:

Problem: X is broken

Solution: do Y and Z to fix X

See https://rfc.zeromq.org/spec:42/C4/ in section 2.3 for details.