title: Sequelize migration fails by cannot read property 'toString' of undefined
body: <p>When trying to run my migration on Sequelize, I am getting the following error;</p>
  <pre><code>== 20170904085107-kognitio-queue: migrating =======
  TypeError: Cannot read property 'toString' of undefined
      at Object.attributeToSQL (/home/vagrant/insights-api/node_modules/sequelize/lib/dialects/mysql/query-generator.js:240:34)
      at Object.attributesToSQL (/home/vagrant/insights-api/node_modules/sequelize/lib/dialects/mysql/query-generator.js:306:45)
      at QueryInterface.createTable (/home/vagrant/insights-api/node_modules/sequelize/lib/query-interface.js:171:38)
      at Object.up (/home/vagrant/insights-api/lib/migrations/20170904085107-kognitio-queue.js:4:31)
      at constructor._exec (/home/vagrant/insights-api/node_modules/umzug/lib/migration.js:104:23)
      at constructor.up (/home/vagrant/insights-api/node_modules/umzug/lib/migration.js:69:17)
      at constructor.&lt;anonymous&gt; (/home/vagrant/insights-api/node_modules/umzug/index.js:124:28)
      at PassThroughHandlerContext.finallyHandler (/home/vagrant/insights-api/node_modules/bluebird/js/release/finally.js:57:23)
      at PassThroughHandlerContext.tryCatcher (/home/vagrant/insights-api/node_modules/bluebird/js/release/util.js:16:23)
      at Promise._settlePromiseFromHandler (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:512:31)
      at Promise._settlePromise (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:569:18)
      at Promise._settlePromise0 (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:614:10)
      at Promise._settlePromises (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:693:18)
      at Promise._fulfill (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:638:18)
      at Promise._resolveCallback (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:432:57)
      at Promise._settlePromiseFromHandler (/home/vagrant/insights-api/node_modules/bluebird/js/release/promise.js:524:17)
  </code></pre>
  <p>The migration file is as follows;</p>
  <pre><code>'use strict';
  module.exports = {
      up: function(queryInterface, Sequelize) {
          return queryInterface.createTable('Kognitio_Queue', {
              queue_id: {
                  allowNull: false,
                  primaryKey: true,
                  type: Sequelize.INTEGER
              },
              queue_user: {
                  allowNull: false,
                  type: Sequelize.STRING(20)
              },
              queue_query: {
                  allowNull: false,
                  type: Sequelize.LONG
              },
              queue_added: {
                  allowNull: false,
                  type: Sequelize.DATETIME,
                  defaultValue: Sequelize.NOW
              },
              queue_executed: {
                  allowNull: true,
                  type: Sequelize.DATETIME
              },
              queue_save_results: {
                  allowNull: false,
                  type: Sequelize.BOOLEAN
              },
              queue_results_path: {
                  allowNull: true,
                  type: Sequelize.TEXT
              }
          });
      },
      down: function(queryInterface, Sequelize) {
          return queryInterface.dropTable('Kognitio_Queue');
      }
  };
  </code></pre>
  <p>And my model file for this is;</p>
  <pre><code>module.exports = (sequelize, DataTypes) =&gt; {
      const Kognitio_Queue = sequelize.define('Kognitio_Queue', {
          queue_id: {
              type: DataTypes.INTEGER,
              allowNull: false,
              primaryKey: true,
          },
          queue_user: {
              type: DataTypes.STRING(20),
              allowNull: false
          },
          queue_query: {
              allowNull: false,
              type: DataTypes.LONG
          },
          queue_added: {
              allowNull: false,
              type: DataTypes.DATETIME
          },
          queue_executed: {
              allowNull: true,
              type: DataTypes.DATETIME
          },
          queue_save_results: {
              allowNull: false,
              type: DataTypes.BOOLEAN
          },
          queue_results_path: {
              allowNull: true,
              type: DataTypes.TEXT
          }
      }, {
          underscored: true,
          freezeTableName: true
      });
      return Kognitio_Queue;
  };
  </code></pre>
  <p>I am at a loss as to what could be causing this error to occur as I have checked these files against other migrations that work successfully and can see no differences between them. I have gone as far as to clear out the entire database and remigrate, but this one is the only one that fails.</p>
  <p>Thanks in advance.</p>