why am I getting this error?

Error using matlab.ui.control.UIControl/set Invalid or deleted object.

Error in GUI>Start_Callback (line 184) set(handles.TrainText,'String','Loading Train Image # ');

where TrainText is an edit text component my code is as follow:

if true
  i = 1;
while (i<=numImage)
  aa = imresize(detect_face(imresize(imread(cell2mat(TrainImages{i,1})),[375,300])),imageSize);
  img(:,i) = aa(:);
  %get(handles.TrainText,'String');
  set(handles.TrainText,'String','Loading Train Image # ');
  drawnow();
%     set(handles.TrainText,'String','Loading Train Image # ');
%     drawnow();
  disp(sprintf('Loading Train Image # %d',i));
  i=i+1;
end
end

[Rik]

This seems to be a duplicate for this.