我正在創建一個簡單的服務器操作，它只打印一個簡單的測試，但是當我運行代碼時，我收到以下錯誤odoo.tools.convert.ParseError: "null value in column "activity_user_type" violates not-null constraintDETAIL:  Failing row contains (617, Confirm, ir.actions.server, null, 552, action, 1, 2020-10-24 02:50:49.149867, 1, 2020-10-24 02:50:49.149867, ir_actions_server, code, 5, 552, null, action = model.print_test(), null, null, null, null, null, null, null, null, null, null, null)." while parsing /home/odoo/odoo12/project1/bearings_module/views/shortfall.xml:52, near代碼<record id="model_custom_shortfall_action_confirm" model="ir.actions.server">        <field name="name">Confirm</field>        <field name="type">ir.actions.server</field>        <field name="model_id" ref="bearings_module.model_custom_shortfall"/>        <field name="binding_model_id" ref="bearings_module.model_custom_shortfall"/>        <field name="state">code</field>        <field name="code">action = model.print_test()</field></record>def print_test(self):        print("Test")