calcZoomStopTable hangs app if z == 0

[jezell]

Sometimes we enter this while loop with a z value of zero which causes the app to hang. Not sure why it is zero, but maybe if it is zero it should not enter the while loop so it doesn't hang?

  void _calcZoomStopTable() {
    _zoomStops.clear();
    double z;
    if (_alternativeFitScale != null &&
        !_areZoomsAlmostIdentical(_alternativeFitScale!, _coverScale!)) {
      if (_alternativeFitScale! < _coverScale!) {
        _zoomStops.add(_alternativeFitScale!);
        z = _coverScale!;
      } else {
        _zoomStops.add(_coverScale!);
        z = _alternativeFitScale!;
      }
    } else {
      z = _coverScale!;
    }
    while (z < PdfViewerController.maxZoom) {
      _zoomStops.add(z);
      z *= 2;
    }
  }

[espresso3389]

Fixed on 1.0.10 and 0.4.46.