title: Ignoring password ' ' on update with Sequelize
body: <p>I need help, I need to check if the password is "EMPTY" in the update clause. If empty, it should update, otherwise not.</p>
  
  <pre><code>import bcrypt from 'bcrypt-nodejs';
  
  module.exports = function (sequelize, DataTypes) {
    const Users = sequelize.define('users', {
      id: {
        type: DataTypes.INTEGER,
        primaryKey: true,
        unique: true,
        autoIncrement: true,
        field: 'id_user_acess'
      },
      username: {
        type: DataTypes.STRING,
        allowNull: true
      },
      nome: {
        type: DataTypes.STRING,
        allowNull: true
      },
      password: {
        type: DataTypes.STRING,
        allowNull: false
      }
    }, {
        tableName: 'tb_user_acess',
        timestamps: false,
        classMethods: {
          generateHash: function(password) {
            return bcrypt.hashSync(password, bcrypt.genSaltSync(10), null);
          },
          comparePassword: function(canditate, password) {
            console.log(canditate);
            console.log(password);
            return bcrypt.compareSync(canditate, password);
          }
        },
        hooks: {
          beforeCreate: function (model) {
            let user = model.dataValues;
            user.password = Users.generateHash(user.password);
            return user;
          },
          beforeUpdate: function (model) {
            let user = model.dataValues;
            if(user.password == ''){
              exclude: user.password;
            }else{
              user.password = Users.generateHash(user.password); 
              console.log(user.password);
            }
  
            return user;
          }
        }
      });
    return Users;
  };
  </code></pre>
  
  <p>I tried to apply something but it did not have much effect
  This is my model with sequelize , plz some light &lt;3</p>