Unable to get output of letters from morse code

Im trying to reverse engineer the morse code encoder i made (which is working fine) but i ran into two problems

    morsecode = {'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..', ...
            '--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-', ...
            '-.--','--..'};
    letter = char('A':'Z');
    userinput = strjoin(strsplit(userinput, ' '));
    for i = 1:length(userinput)
        [~, index] = ismember(userinput(i), morsecode);
        if index > 0
            moutput = [moutput ' ' letter{i}]
        end  
    end

    set(handles.morse, 'String' , moutput);

in this example the letter{i} is the part which an error occurs, and when i change it to () instead of {} an output comes out, but its just A B C D E F G.....Z regardless of the morsecode input i enter....may i know if there is a problem wiht my logic? thanks