Hopefully fix righhtpanel crash

The right panel wearns many hats, and only one of those hats comes
with a room prop, so make sure it's there.

Author: dbkr

src/components/structures/RightPanel.js

@@ -3,7 +3,7 @@ Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2017, 2018 New Vector Ltd
 Copyright 2019 Michael Telatynski <[email protected]>
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2019, 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -162,7 +162,7 @@ export default class RightPanel extends React.Component {
     }
 
     onRoomStateMember(ev, state, member) {
-        if (member.roomId !== this.props.room.roomId) {
+        if (!this.props.room || member.roomId !== this.props.room.roomId) {
             return;
         }
         // redraw the badge on the membership list