fix fileset sorting

hyrax/app/models/file_set_fast_load_metadata.rb

 class FileSetFastLoadMetadata < ActiveRecord::Base
   scope :sort_and_filter_by_title_and_source, ->(work_source_identifier) {
     where(work_source_identifier: work_source_identifier)
-    .sort_by { |item| item.file_set_title.downcase.scan(/(\d+)|(\D+)/).map { |n, s| n ? n.to_i : s } }
+    .sort_by { |item| item.file_set_title.downcase.gsub(/[^a-zA-Z0-9]/, '0').split(/(\d+)/).map { |s| s.match(/\d+/) ? s.to_i : s } }
   }
 end
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