Avoid unnecessary buildup of empty arrays that have to be removed later

Author: Kevin Paulisse

lib/octocatalog-diff/catalog.rb

@@ -191,6 +191,7 @@ def validate_references
           next unless x.key?('parameters')
           next unless x['parameters'].key?(r)
           missing_resources = remove_existing_resources(x['parameters'][r])
+          next unless missing_resources.any?
           missing << missing_resources.map { |missing_target| { source: x, target_type: r, target_value: missing_target } }
         end
       end