Save the results of a non scalar struct

I've the following function

function fun(i)
var =  true
if var
    ss(i).bv = rand(10,1)
    
    if i  == 4
        pwd
        save(fullfile(pwd, 'ss.mat'), 'ss');    
    end
end

The above function is called as below

for i = 1:4
i
fun(i)
end

The result is loaded,

l = load('ss.mat')
l.ss.bv

ans =

     []


ans =

     []


ans =

     []


ans =

    0.8217
    0.4299
    0.8878
    0.3912
    0.7691
    0.3968
    0.8085
    0.7551
    0.3774
    0.2160

I am not sure why the first there indices are empty. I want to store the results for all i.

Any suggestions?

[per isakson]

Identical to https://se.mathworks.com/matlabcentral/answers/509124-save-a-non-scalar-struct ?