vi: failure to open file is not an error when initialising buffer

vi: failure to open file is not an error when initialising buffer

Commit 32afd3a introduced these regressions on the master branch:

Starting vi with no filename on the command line gives the status message
"'(null)' Bad address" instead of "- No file 1/1 100%".

Starting vi with a non-existent file on the command line gives the status
message "'new.txt' No such file or directory" instead of "- new.txt 1/1 100%"

Signed-off-by: Ron Yorston <rmy@tigress.co.uk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>