refdb_fs: remove unnecessary check for NULL
refdb_fs: remove unnecessary check for NULL

The fail-label of `reflog_parse` explicitly checks the entry
poitner for NULL before freeing it. When we jump to the label the
variable has to be set to a non-NULL and valid pointer though: if
the allocation fails we immediately return with an error code and
if the loop was not entered we return with a success code,
withouth executing the label's code.

Remove the useless NULL-check to silence Coverity.

saurabhsuniljain/libgit2,leoyanggit/libgit2,leoyanggit/libgit2,stewid/libgit2,stewid/libgit2,jeffhostetler/public_libgit2,leoyanggit/libgit2,stewid/libgit2,stewid/libgit2,Corillian/libgit2,Corillian/libgit2,saurabhsuniljain/libgit2,Corillian/libgit2,saurabhsuniljain/libgit2,joshtriplett/libgit2,joshtriplett/libgit2,Corillian/libgit2,jeffhostetler/public_libgit2,jeffhostetler/public_libgit2,Corillian/libgit2,saurabhsuniljain/libgit2,saurabhsuniljain/libgit2,joshtriplett/libgit2,leoyanggit/libgit2,jeffhostetler/public_libgit2,joshtriplett/libgit2,joshtriplett/libgit2,leoyanggit/libgit2,Corillian/libgit2,leoyanggit/libgit2,stewid/libgit2,jeffhostetler/public_libgit2,jeffhostetler/public_libgit2,saurabhsuniljain/libgit2,joshtriplett/libgit2,stewid/libgit2