fix generate

lib/submissions/generate_result_attachments.rb

@@ -602,6 +602,8 @@ module Submissions
             cell_valign = field.dig('preferences', 'valign').to_s.presence_in(TEXT_VALIGNS) || 'center'
             cell_layouter = cell_layouters[cell_valign]
 
+            value = value.to_s
+
             if (mask = field.dig('preferences', 'mask').presence)
               value = TextUtils.mask_value(value, mask)
             end