I'm creating a simple api witch verify if the username and/or password are in the DB and if they are correct.

When I post correct data, it works. When I post a wrong password, it also works. But when I post a wrong username, my condition don't jump to the else. If the username is wrong, it means it is not in the DB. But here, it is like if it was in the DB, but he is not, so I get an error : " TypeError: Cannot read properties of undefined (reading 'Username') "

Here the code

app.post('/login', function(req, res) {
    (async () => {
    const bcrypt = require('bcrypt')

    
    try {
        username = req.query.username
        password = req.query.password

        let salt = await bcrypt.genSalt(10)
        let hash = await bcrypt.hash(password, salt)

        db_conn.getConnection( (err, conn) => {
            
            if(err) throw err;
            
            conn.query("SELECT * FROM mod803_appusers WHERE Username=? ", [username], (err, rows) => {

                //Problem here : when I put a wrong password, it's ok, this condition works because there is a password, and if bcrypt.compare is true, it sends response, but if it's false, it sends 'Wrong password'.
                //But if the Username is Wrong, it means there is no username in the DB. So here, I want this condition jump to the else : 'Incorrect username' but it doesn't.

                if(rows[0]['Username'] && rows[0]['Password']) {
                    bcrypt.compare(password, rows[0]['Password'], function(err, result) {
    
                        if(result){
                            
                            res.send({"table": rows});
    
                        } else {
                            res.send("Wrong password");
    
                    }}); 
                    

                } else {
                    res.send('Incorrect username');

                }
                
            })
            
        })

    } catch (error) {
        console.log(error.message)
    }
})()

})

Thanks