[React Native][Pokes Dashboard] Fix crash

Libraries/Components/Touchable/TouchableHighlight.js

@@ -181,6 +181,10 @@ var TouchableHighlight = React.createClass({
   },
 
   _showUnderlay: function() {
+    if (!this.isMounted()) {
+      return;
+    }
+
     this.refs[UNDERLAY_REF].setNativeProps(this.state.activeUnderlayProps);
     this.refs[CHILD_REF].setNativeProps(this.state.activeProps);
     this.props.onShowUnderlay && this.props.onShowUnderlay();