In TDirectoryFile::Save, iterate while allowing concurrent remove.
In TDirectoryFile::Save, iterate while allowing concurrent remove.

When allowing concurrent remove, the link's element might be nullptr before the end of the list

root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,karies/root,karies/root,olifre/root,karies/root,olifre/root,olifre/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,karies/root,karies/root