Error while evaluating uicontrol Callback

Hi, i got this error when try to run the program. Can anyone explain what is wrong?

Reference to non-existent field 'txtInfo'.

Error in realtime21>btnPreviewVideo_Callback (line 100) set(handles.txtInfo, 'string', errorMessage);

Error in gui_mainfcn (line 96) feval(varargin{:});

Error in realtime21 (line 42) gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)realtime21('btnPreviewVideo_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

Below is the coding for my gui

if true
  % --- Executes on button press in btnPreviewVideo.
function btnPreviewVideo_Callback(hObject, eventdata, handles)
% hObject    handle to btnPreviewVideo (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
  % Initialize the video camera.
  global vidobj;  % Video camera object.
  try
    % Initialize Logitech webcam
    vidobj = videoinput('winvideo', 1, 'YUY2_320x240');
    if ~isempty(vidobj)
      src = getselectedsource(vidobj);
      vidobj.FramesPerTrigger = 1;
      axes(handles.axesImage);
      hImage = findobj(handles.axesImage, 'Type', 'image');
      preview(vidobj, hImage);
%       src.ZoomMode = 'manual';
      % Turn on the live video preview.  Display the bounding box over it if there is one selected.
      TurnOnLiveVideo(handles);
    end
    % Turn on the live video preview.  Display the bounding box over it if there is one selected.
    TurnOnLiveVideo(handles);
  catch ME
    errorMessage = sprintf('Error in function logitech_webcam_OpeningFcn.\nNo Logitech webcam detected!\n\nError Message:\n%s', ME.message);
    set(handles.txtInfo, 'string', errorMessage);
    uiwait(warndlg(errorMessage));
  end

if true
  function TurnOnLiveVideo(handles)
  global vidobj;  % Video camera object.
  % Bail out if there is no video object class instantiated.
  if isempty(vidobj), return, end;
  % Switch the current graphic axes to handles.axesImage.
  % This is where we want the video to go.
  axes(handles.axesImage);
  % Reset image magnification. Required if you ever displayed an image
  % in the axes that was not the same size as your webcam image.
  hold off;
  axis auto;  
  % Get the handle to the image in the axes.
  hImage = findobj(handles.axesImage, 'Type', 'image');
  % Turn on the live video.
  preview(vidobj, hImage);
  % Put hold on so that displaying our bounding box doesn't blow away the image.
  hold on;
  % Retrieve our x,y coordinates of the bounding box corners.
  GetImageMask(handles);
  % They have been previously set elsewhere as global variables.
  global maskVerticesXCoordinates;
  global maskVerticesYCoordinates;
  if ~(isempty(maskVerticesXCoordinates) || isempty(maskVerticesYCoordinates))
    % If the bounding box coordinates exist,
    % plot the bounding box over the live video.
    plot(maskVerticesXCoordinates, maskVerticesYCoordinates);
  end
  
%   stoppreview(vidobj);
return; % from TurnOnLiveVideo
end

Thanks