backup crash: "panic: strings: negative Repeat count"

Magma backup tests failed on build 7.0.0-4226, and the issue is reproducible. The cbbackupmgr collect info log file is attached.

2021-01-19T17:44:40 [INFO] running ./opt/couchbase/bin/cbbackupmgr config --archive /workspace/backup --repo default

2021-01-19T17:44:40 [INFO] Running: ./opt/couchbase/bin/cbbackupmgr backup --archive /workspace/backup --repo default --host http://172.23.97.26 --username Administrator --password password --threads 16 --storage sqlite

Fatal error: local() encountered an error (return code 2) while executing './opt/couchbase/bin/cbbackupmgr backup --archive /workspace/backup --repo default --host http://172.23.97.26 --username Administrator --password password --threads 16 --storage sqlite'

Aborting.

Build: 7.0.0-4226

Job: http://perf.jenkins.couchbase.com/job/rhea-5node2/682/ 

Logs:

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-5node2-682/172.23.97.26.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-5node2-682/172.23.97.27.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-5node2-682/172.23.97.28.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-5node2-682/172.23.97.29.zip