I found a temporary fix for the WT error with the help of ChatGPT.
Replace the codes on line 119 in JokerTextbox.rpy in the JokerMod folder:
screen say(who, what):
    style_prefix "say"
    ###Textbox transparency
    $ l_alpha = 1 - float(g_textbox_transparency) / 100
    ###
    window:
        id "window"
        #######Textbox transparency
        background Image(im.Alpha("gui/textbox.png", l_alpha), xalign=0.5, yalign=1.0)
        ######
        if who is not None:
            window:
                id "namebox"
                style "namebox"
                text who id "who"
        if persistent.say_window_alpha < 0.6:
            text what id "what" size persistent.pref_text_size outlines [(4, "#000", 0, 0)]
        else:
            text what id "what" size persistent.pref_text_size outlines [(4, "#000", 0, 0)]
    ## If there's a side image, display it above the text. Do not display on the
    ## phone variant - there's no room.
    if not renpy.variant("small"):
        add SideImage() xalign 0.0 yalign 1.0
With
screen say(who, what):
    style_prefix "say"
    ###Textbox transparency
    $ l_alpha = 1 - float(g_textbox_transparency) / 100
    ###
    window:
        id "window"
        #######Textbox transparency
        background Image(im.Alpha("gui/textbox.png", l_alpha), xalign=0.5, yalign=1.0)
        ######
        if who is not None:
            window:
                id "namebox"
                style "namebox"
                text who id "who"
        if persistent.say_window_alpha is not None and persistent.say_window_alpha < 0.6:
            text what id "what" size persistent.pref_text_size outlines [(4, "#000", 0, 0)]
        else:
            text what id "what" size persistent.pref_text_size outlines [(4, "#000", 0, 0)]
    ## If there's a side image, display it above the text. Do not display on the
    ## phone variant - there's no room.
    if not renpy.variant("small"):
        add SideImage() xalign 0.0 yalign 1.0
Save and it should work.
I have no coding skills in rpy so I just fed the AI the information needed to fix the error. So it might not work for you.
There seems to be issues trying to load saves but if you rollback it should lead you to the choices that you saved.