message: null guard group inviter for corrupted groups
diff: @@ -1003,9 +1003,10 @@ export default createReactClass({
  this.state.inviterProfile.avatarUrl, 36, 36,
  ) : null;
  - let inviterName = group.inviter.userId;
  + const inviter = group.inviter || {};
  + let inviterName = inviter.userId;
  if (this.state.inviterProfile) {
  - inviterName = this.state.inviterProfile.displayName || group.inviter.userId;
  + inviterName = this.state.inviterProfile.displayName || inviter.userId;
  }
  return <div className="mx_GroupView_membershipSection mx_GroupView_membershipSection_invited">
  <div className="mx_GroupView_membershipSubSection">
  @@ -1016,7 +1017,7 @@ export default createReactClass({
  height={36}
  />
  { _t("%(inviter)s has invited you to join this community", {
  - inviter: inviterName,
  + inviter: inviterName || _t("Someone"),
  }) }
  </div>
  <div className="mx_GroupView_membership_buttonContainer">
  