Recent runs of GC for rawhide are failing because images in quay.io were deleted in a previous run but the build.json was never updated to reflect that. [1]
Update the code to check if the image is already non-existent and not fail on this case [2]

[1] https://jenkins-fedora-coreos-pipeline.apps.ocp.fedoraproject.org/job/garbage-collection/310/consoleFull
[2]