Make the webapp robust to not receiveing a position. (#4802)

webapp/components/user_profile.jsx

@@ -182,8 +182,8 @@ export default class UserProfile extends React.Component {
 
         dataContent.push(webrtc);
 
-        const position = this.props.user.position.substring(0, Constants.MAX_POSITION_LENGTH);
-        if (position) {
+        if (this.props.user.position) {
+            const position = this.props.user.position.substring(0, Constants.MAX_POSITION_LENGTH);
             dataContent.push(
                 <div
                     data-toggle='tooltip'