Issues with marks in Eww

[Francisco Javier Dorado Martínez <javier@xxxxxxxxxxx>]

Hi all
I am having issues with marks trying to read a book on Emacspeak.
I place a mark with m key, then try to go to that mark with c-x, r, e
and I get following:
Wrong type argument: arrayp, nil
I enter a string for the mark, also have tried with a number but no
luck.
Is something wrong? I am using this feature incorrectly?
Many thanks,
Regards
Javier