This allows a refresh on a non-existent or empty state file. We changed
this in 0.9.0 to error which seemed reasonable but it turns out this
complicates automation that runs refresh since it now needed to
determine if the state file was empty before running.
Its easier to just revert this into a warning with exit code zero.
The reason this changed is because in 0.8.x and earlier, the output
would be simply empty with exit code zero which seemed odd.
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