protect against posible segv on rename with eio

this MIGHT fix https://phab.enlightenment.org/T45 but i can't reproduce
to confirm, but reading a
backtrace indicates this could have been the issue. it looks like
there is room for a dangling pointer anyway, so fix.

Backport from commit 323f293ab538ffc7431f6598736963a834c4f880
on https://git.enlightenment.org/core/efl.git