pr-pull: fix empty workflow check

workflow_run is an array, which first element is the json
returned by the github API. We need to check that first element
if we want to know if the workflow exists.

Library/Homebrew/dev-cmd/pr-pull.rb

@@ -419,9 +419,10 @@ module Homebrew
             )
             if args.ignore_missing_artifacts.present? &&
                args.ignore_missing_artifacts.include?(workflow) &&
-               workflow_run.empty?
+               workflow_run.first.blank?
               # Ignore that workflow as it was not executed and we specified
               # that we could skip it.
+              ohai "Ignoring workflow #{workflow} as requested by --ignore-missing-artifacts"
               next
             end