CLDSRV-922: do not reference null version from master in null-key mode#6190

bert-e merged 2 commits into

development/9.3scality/cloudserver:development/9.3from

bugfix/CLDSRV-922-backbeat-null-version-masterscality/cloudserver:bugfix/CLDSRV-922-backbeat-null-version-masterCopy head branch name to clipboard