small error in get_mean_amplitude()

[LeonvonHaugwitz]

Hi Eric,

many thanks for your work! There is a easy to fix error in get_mean_amplitude() in line 102 when specifying to export means of a specific cluster of an effect. Matlab throws the error in line 118 when checking length(clust_info.null_test).

% Assign variables

 effect = p.Results.effect;
 clust_id = p.Results.clust_id;
 bins = p.Results.bins;
 output_file = p.Results.output_file;
 results = GNDorGRP.F_tests(test_id);
    
if isempty(effect)
        null_test = results.null_test;
        clust_info = results.clust_info;
else
        null_test = results.null_test.(effect);
        clust_info = results.null_test.(effect);            [ should be:  clust_info = results.clust_info.(effect); ]
end