plumbing/object: don't assign err from ForEach loop
plumbing/object: don't assign err from ForEach loop

Since we don't check the value anyway, as it can't possibly be anything but nil.

Signed-off-by: Christian Muehlhaeuser <0a362b7528cb3a818f8ef2ffbc5db2ca2860109d@gmail.com>
(cherry picked from commit 293e70fbceb5c81f33a96d5705f10785c6063db9)

src-d/go-git,mcuadros/go-git,go-git/go-git,go-git/go-git,src-d/go-git,mcuadros/go-git