title: Warning: isMounted(...) is deprecated in plain Javascript Classes
body: <p>I am implementing 2 screens using react-navigation. But I got the warning below while navigating to the second page:</p>
  
  <blockquote>
    <p>Warning: isMounted(...) is deprecated in plain Javascript Classes. Instead, make sure to clean up subscriptions and pending requests in componentWillUnmount to prevent memory leaks.</p>
  </blockquote>
  
  <p>Versions:</p>
  
  <ul>
  <li>react:             16.3.1</li>
  <li>react-native:      0.55.2</li>
  <li>react-navigation:  1.5.11</li>
  <li>util:              0.10.3</li>
  </ul>
  
  <p><strong>Login.js</strong></p>
  
  <pre><code>import React, { Component } from 'react';
  import { Text, View, Image, TextInput, TouchableOpacity } from 'react-native';
  import styles from "./styles";
  
  export default class Login extends Component {
      constructor(props) {
      super(props);
  }
  
  render() {
      const { navigate } = this.props.navigation;     
      return (
          &lt;View style={styles.container}&gt;         
              &lt;View style={styles.formContainer}&gt;                 
                  &lt;TouchableOpacity style={styles.button} onPress={()=&gt; navigate('Home')} &gt;
                      &lt;Text style={styles.buttonText}&gt;LOGIN&lt;/Text&gt;
                  &lt;/TouchableOpacity&gt;
              &lt;/View&gt;
          &lt;/View&gt;
      )
  }
  </code></pre>
  
  <p><strong>Home.js</strong></p>
  
  <pre><code>import React, { Component } from 'react';
  import { Text, View } from 'react-native';
  import styles from "./styles";
  
  export default class Home extends Component {
      constructor(props) {
          super(props);
      }
      render() {
          const { navigate } = this.props.navigation;
          return(
              &lt;View style={styles.container}&gt;         
                  &lt;Text&gt;Home Screen&lt;/Text&gt;
              &lt;/View&gt;
          )
      }
  }
  </code></pre>
  
  <p>What am I missing here?</p>