For MATLAB mirfeatures function I get the valid interpreter syntax error

Question

Following this manual page 195, I run the f = mirfeatures(a), where a is a miraudio('mysong.wav') object. Then I want to get the results stored in f. However, I get the following error after this command: f.dynamics.rms{1}

Brace indexing is not supported for variables of this type.

and the following warning after this command: f.dynamics.rms

Warning: Error updating Text.

 String scalar or character vector must have valid interpreter syntax:
RMS energy, E:\Video-Project\Watches\audio_320k_44100_1122002.wav
 
> In defaulterrorcallback (line 12)
In mirscalar/display_figure (line 390)
In mirscalar/display (line 10) 

I need to mention that when I run mirrms(a). I get no warning. The mentioned commands are on the manual page 195. Also. f.dynamics.rms generates a figure.

Here is the code and the audio file:

a = miraudio('audio_320k_44100_1122002.wav');
f = mirfeatures(a);
f.dynamics.rms;
f.dynamics.rms{1};