Fix parsing of id for riiif viewer

hyrax/config/initializers/riiif.rb

@@ -14,7 +14,13 @@ ActiveSupport::Reloader.to_prepare do
   end
 
   Riiif::Image.file_resolver.id_to_uri = lambda do |id|
-    fs_id = id.sub(/\A([^\/]*)\/.*/, '\1')
+    # id is of the pattern
+    # /images/<fileset_id>/files/<uuid>/fcr:versions/version1/full/200,/0/default.jpg or
+    # <fileset_id>/files/<uuid>/fcr:versions/version1/full/200,/0/default.jpg
+    fs_id = id
+    fs_id = fs_id.gsub(/^\//, '') if fs_id.start_with?('/')
+    fs_id = fs_id.gsub(/^images\//, '') if fs_id.start_with?('images/')
+    fs_id = fs_id.split('/')[0] if fs_id.include?('/')
     s3_file_url(fs_id)
   end
 
@@ -26,10 +32,11 @@ ActiveSupport::Reloader.to_prepare do
   Riiif::Engine.config.cache_duration = 365.days
 
   def s3_file_url(fs_id)
+    return "" unless fs_id
+    file_set = FileSet.find(fs_id)
+    return "" unless file_set.present?
     s3 = S3StorageService.new
     s3.init_client
-    
-    file_set = FileSet.find(fs_id)
     bucket_name = s3.sanitise_name(file_set.parent_works.first.id)
     file_key = file_set.title.first
     s3.presigned_url_for_download(bucket_name, file_key)