title: Brain.js return null, NaN values in training
body: <p>I'm using Brain.js to make Gomoku AI, and even though the size of Input is fixed at 225, it's not trained. (All values are null, training error is only NaN.)</p>
  <p><a href="https://i.stack.imgur.com/PNeac.png" rel="nofollow noreferrer">Picture of trained model .json</a></p>
  <p>And is it right to put '00' in the process of filling data to flatten Input's size to 225?<br />
  The Training Data is written like as follows:</p>
  <pre><code>[
    {
      input: [
        '00', '00', '00', '00', ... fill '00' in to empty space to fit 225 size
      ],
      output: { '88': 1 } //The winning player's move have 1 value
    },
    {
      input: [
        '88', '00', '00', '00', ... fill '00' in to empty space to fit 225 size
      ],
      output: { '89': 0 } //The losing player's move have 0 value
    },
    {
      input: [
        '88', '89', '00', '00', ... fill '00' in to empty space to fit 225 size
      ],
      output: { '68': 1 }
    }
  ] 
  
  </code></pre>
  <p>How should I fix it to make the train successfully?<br />
  <a href="https://github.com/gkfyddl2662/Brain.Gomoku" rel="nofollow noreferrer"><strong>and Here's my code.</strong></a></p>
  <p>and sorry for my bad English.</p>