message: Fix sign in / up links on previewed rooms
  They errored because the out-of-band data was assumed to be non-null,
  but that's only present for 3rd party invites.
diff: @@ -266,9 +266,9 @@ export default createReactClass({
  params: {
  email: this.props.invitedEmail,
  signurl: this.props.signUrl,
  - room_name: this.props.oobData.room_name,
  - room_avatar_url: this.props.oobData.avatarUrl,
  - inviter_name: this.props.oobData.inviterName,
  + room_name: this.props.oobData ? this.props.oobData.room_name : null,
  + room_avatar_url: this.props.oobData ? this.props.oobData.avatarUrl : null,
  + inviter_name: this.props.oobData ? this.props.oobData.inviterName : null,
  }
  };
  },
  