imcontrast Data range vs Display range

I'm using imcontrast to interactively select the best min and max values for the histogram adjustment, with certain pictures I get this error

it's basically saying that the data range and the diplay range are somehow mismatched and need to be changed, so after I do the selection and I'm satisfy with the results and when I close the window(I have a function that extract max and min values from imcontrast once the user closes the window) and the image goes completely black, because apperently the numbers that I'm getting from imcontrast are the ones changed for the display issue.

any Idea on what to do to fix this?

here is my code

function adjust_contrast_Callback(hObject, eventdata, handles)
global icontrast;
guidata(hObject, handles);
axes(handles.axes1);
h = imshow(handles.I);
dbh = imcontrast(h);
total = str2double(get(findobj(dbh, 'tag', 'window max edit'), 'String'));
disp(total);
set(dbh, 'CloseRequestFcn', @(s,e)getValues(s))
waitfor(dbh);
icontrast(1) = icontrast(1)/total;
icontrast(2) = icontrast(2)/total;
disp(icontrast);
handles.I = imadjust(handles.I,icontrast);
imshow(handles.I);
guidata(handles.figure1,handles);
h = datacursormode;
set(h,'DisplayStyle','datatip',...
    'SnapToDataVertex','off','Enable','on')

function getValues(dbh)
    global icontrast;
    window_min = str2double(get(findobj(dbh, 'tag', 'window min edit'), 'String'));
    window_max = str2double(get(findobj(dbh, 'tag', 'window max edit'), 'String'));
    icontrast = [window_min window_max];
    disp(icontrast);
    delete(gcf);

I'm also using icontrast here as a global variable which is not good practice, but it was because I couldn't figure out how to pass variables between that function and any other callback function, if you have an idea on how to do it, that would also be nice!

thank you!