message: Add a bit more safety around breadcrumbs
  Fixes
diff: @@ -126,6 +126,7 @@ export default class AccountSettingsHandler extends MatrixClientBackedSettingsHa
  if (!content || !content['recent_rooms']) {
  content = this._getSettings(BREADCRUMBS_LEGACY_EVENT_TYPE);
  }
  + if (!content) content = {}; // If we still don't have content, make some
  content['recent_rooms'] = newValue;
  return MatrixClientPeg.get().setAccountData(BREADCRUMBS_EVENT_TYPE, content);
  @@ -167,7 +168,7 @@ export default class AccountSettingsHandler extends MatrixClientBackedSettingsHa
  // This seems fishy - try and get the event for the new rooms
  const newType = this._getSettings(BREADCRUMBS_EVENT_TYPE);
  if (newType) val = newType['recent_rooms'];
  - else val = event.getContent()['rooms'];
  + else val = event.getContent()['rooms'] || [];
  } else if (event.getType() === BREADCRUMBS_EVENT_TYPE) {
  val = event.getContent()['recent_rooms'];
  } else {
  