message: [avahi] check if mGroup is nil before commit
  `PublisherAvahi::CreateGroup` may not succeed.
diff: @@ -442,7 +442,10 @@ void PublisherAvahi::HandleClientState(AvahiClient *aClient, AvahiClientState aS
  mState = kStateReady;
  CreateGroup(aClient);
  mStateHandler(mContext, mState);
  + if (mGroup)
  + {
  avahi_entry_group_commit(mGroup);
  + }
  break;
  case AVAHI_CLIENT_FAILURE:
  