Flask，WTForms:编辑和创建表单规则不同时出错

from flask import Flask, render_template, request
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, Optional

app = Flask(__name__)
app.config['SECRET_KEY'] = 'your_secret_key'

class UserForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    email = StringField('Email', validators=[DataRequired()])
    password = PasswordField('Password', validators=[Optional()])
    submit = SubmitField('Submit')

    def __init__(self, *args, **kwargs):
        super(UserForm, self).__init__(*args, **kwargs)
        self.is_editing = kwargs.get('is_editing', False)
        if self.is_editing:
            self.password.validators = [Optional()]
            self.password.render_kw = {'disabled': True}

@app.route('/create', methods=['GET', 'POST'])
def create():
    form = UserForm()
    if form.validate_on_submit():
        # 处理创建逻辑
        pass
    return render_template('create.html', form=form)

@app.route('/edit/<int:user_id>', methods=['GET', 'POST'])
def edit(user_id):
    form = UserForm(is_editing=True)
    if form.validate_on_submit():
        # 处理编辑逻辑
        pass
    return render_template('edit.html', form=form)

if __name__ == '__main__':
    app.run(debug=True)