fix(form): Add missing key field in settings-selector-panel

Author: David Emory

lib/components/form/settings-selector-panel.js

@@ -254,7 +254,7 @@ class SettingsSelectorPanel extends Component {
             </Col>
             <Col xs={12} style={{ textAlign: 'center' }}>
               {transitModes.map((mode, k) => {
-                return (<div style={{ display: 'inline-block', width: 64 }}>
+                return (<div style={{ display: 'inline-block', width: 64 }} key={k}>
                   <ModeButton
                     enabled={modeHasTransit}
                     active={this._modeIsActive(mode)}