Allow prepopulated metadata to be empty
What does this MR do?
Today we had two coordinated pipelines run simultaneously due to an issue with our runner manager.
As a result, we tagged a coordinator pipeline but never wrote metadata, so on our next run we fetched the previous tag, tried to prepopulate metadata from it, and came up empty, throwing a NoMethodError
.
This works around this scenario by allowing metadata to be empty.
Original error: https://ops.gitlab.net/gitlab-org/release/tools/-/jobs/4169348