Error using * ?

hi. i wrote these codes. but it gives me error. plz help me. how can i fix this error?

if handles.plot2.Value==1
    var1=get(handles.varible1,'string');
    range1=str2num(get(handles.range1,'string'));
    H=str2num(get(handles.hamiltonian,'string'));
    
    if handles.thermal.Value==1
        sx=[0 1;1 0];
        sy=[0 -1i;1i 0];
        sz=[1 0;0 -1];
        s=kron(sy,sy);
        ro = expm(-H/T)/trace(expm(-H/T));
        la = real(sqrt(eig(ro*s*conj(ro)*s)));
        co=@(var1) max(0,2*max(la)-sum(la));
        var1=range1;
        for k = 1:numel(range1)
            cov(k) = co(range1(k));
        end
        axes(handles.axes1);
        plot(range1, cov)
    end
end

%the error is
%matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)quantum('temperature_CreateFcn',hObject,eventdata,guidata(hObject)) 
%Error using  * 
%Inner matrix dimensions must agree.

%Error in quantum>run_Callback (line 225)
 %       la = real(sqrt(eig(ro*s*conj(ro)*s)));

%Error in gui_mainfcn (line 95)
 %       feval(varargin{:});

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

%Error in
%matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)quantum('run_Callback',hObject,eventdata,guidata(hObject)) 
%Error while evaluating UIControl Callback.

[Star Strider]

The error is clear menough:

Error using  * 
Inner matrix dimensions must agree.
Error in quantum>run_Callback (line 225)
       la = real(sqrt(eig(ro*s*conj(ro)*s)));

Examine the sizes of the components of that expression to see what the problem is.

[Walter Roberson]

Two many variables we do not know the size of.

Also, we have no reason to expect that the variable J will have a value at that point, so the str2num() is likely to return []