make shell script more robust to missing files
make shell script more robust to missing files

e.g. cmti in 4.00.1

djs55/ocaml-conduit,avsm/ocaml-conduit,mirage/ocaml-conduit,rgrinberg/ocaml-conduit,edwintorok/ocaml-conduit,rgrinberg/ocaml-conduit,djs55/ocaml-conduit,Drup/ocaml-conduit,samoht/ocaml-conduit,samoht/ocaml-conduit,edwintorok/ocaml-conduit,Drup/ocaml-conduit