Passport ReferenceError: err is not defined - node.js

Question

I want to do a login Form and I did nearly everything fixed but if I registered successfully and I want to log in, it throws either if the password is correct or incorrect:
UnhandledPromiseRejectionWarning: ReferenceError: err is not defined
So i looked up and the errormessage is this: bcrypt.compare(password, user.password, (err, isMatch => {
If the username is wrong or doesnt exist it just redirect me with an error message, like I programmed it.
Full controller/passport.js file
module.exports = function (passport) {
passport.use(
new LocalStrategy({ usernameField: 'username' }, (username, password, done) => {
// Matching
User.findOne({ username: username })
.then(user => {
if (!user) {
return done(null, false)
}
bcrypt.compare(password, user.password, (err, isMatch => {
if (err) throw err;
if (isMatch) {
return done(null, user);
} else {
return done(null, flase, { message: 'Passwort nicht korrekt' })
}
}))
})
})
)
passport.serializeUser( function (user, done) {
done(null, user.id);
});
passport.deserializeUser( function (id, done) {
User.findById(id,function (err, user) {
done(err, user);
});
});
}
I include this module into my routes.js
// Login
router.get('/', forwardAuthenticated, (req, res) => {
res.render('login/index');
})
router.post('/', (req, res, next) => {
passport.authenticate('local', {
successRedirect: '../admin',
failureRedirect: '/login'
})(req, res, next)
})
app.js
require('./controller/passport')(passport);
app.use(passport.initialize());
app.use(passport.session());
I tried to remove the err but then false wouldnt be defined, I looked up the passport docu but I havnt found anything, any ideas?
I use express, passport, passport-local, mongoose