title: Cannot open phone call with Linking.openURL
body: <h2>Description</h2>
  
  <p>Cannot open phone call with Linking.openURL('tel:+123456789') </p>
  
  <h2>Environment</h2>
  
  <p>Environment:
    OS: macOS High Sierra 10.13.4
    Node: 8.5.0
    Yarn: Not Found
    npm: 5.8.0
    Watchman: Not Found
    Xcode: Xcode 9.3 Build version 9E145
    Android Studio: 2.3 AI-162.4069837</p>
  
  <p>Packages: (wanted => installed)
    react: 16.3.1 => 16.3.1
    react-native: <a href="https://github.com/expo/react-native/archive/sdk-27.0.0.tar.gz" rel="noreferrer">https://github.com/expo/react-native/archive/sdk-27.0.0.tar.gz</a> => 0.55.2
    expo: 27.0.1,</p>
  
  <h2>Steps to Reproduce</h2>
  
  <pre><code>import ...
  export default class App extends React.Component {
  
  _pressCall=()=&gt;{
      const url='tel:+123456789'
      Linking.openURL(url)
  }
  
  render() {
      return (
          &lt;View style={styles.container}&gt;
              &lt;Button title='call' onPress={this._pressCall}/&gt;
          &lt;/View&gt;
      );
  }
  }
  </code></pre>
  
  <p><a href="https://snack.expo.io/@kikoololmdrxdd/test-linking-phone-call" rel="noreferrer">https://snack.expo.io/@kikoololmdrxdd/test-linking-phone-call</a></p>
  
  <h2>Expected Behavior</h2>
  
  <p>open phone call</p>
  
  <h2>Actual Behavior</h2>
  
  <pre><code>[Android]Error message
  attempt to invoke virtual method 'boolean java.lang.string.endsWith(java.
  lang.String)' on a null object reference
  </code></pre>