fix school daily report task

app/tasks/statistic_school_daily_report_task.rb

@@ -41,9 +41,12 @@ class StatisticSchoolDailyReportTask
         shixun_increase_count: shixun_count, active_user_count: active_user_count, date: current_date
       }
       report = SchoolDailyReport.create!(create_params)
-      values = '(' + active_user_ids.join(", #{report.id}),(") + ", #{report.id})"
-      user_sql = "INSERT INTO school_daily_active_users(user_id, school_daily_report_id) VALUES#{values}"
-      SchoolDailyActiveUser.connection.execute(user_sql)
+
+      if active_user_ids.present?
+        values = '(' + active_user_ids.join(", #{report.id}),(") + ", #{report.id})"
+        user_sql = "INSERT INTO school_daily_active_users(user_id, school_daily_report_id) VALUES#{values}"
+        SchoolDailyActiveUser.connection.execute(user_sql)
+      end
     end
   end