message: Add null check for channelData
  No null check for channelData looks like breaking changes as sometime it
  will not be present when we try to use context.sendActivity.
diff: @@ -398,7 +398,7 @@ export class WebexAdapter extends BotAdapter {
  if (activity.conversation && activity.conversation.parentId) {
  // @ts-ignore ignore this webex specific field
  message.parentId = activity.conversation.parentId;
  - } else if (activity.channelData.parentId) {
  + } else if (activity.channelData && activity.channelData.parentId) {
  message.parentId = activity.channelData.parentId;
  }
  