调整

app/services/export_shixun_report_service.rb

@@ -10,7 +10,7 @@ class ExportShixunReportService
   end
 
   def filename
-    @_filename ||= "#{homework.name}-#{work.user.user_extension&.student_id}-#{work.user.real_name}.pdf".gsub(' ', '-').gsub('/', '_')
+    @_filename ||= "#{homework.name}-#{work.user&.student_id}-#{work.user.real_name}.pdf".gsub(' ', '-').gsub('/', '_')
   end
 
   def prepare_binding