squirrelmail spell checker (html_mail) plugin

We're running the squirrelmail html_mail plugin that uses FCKeditor.

http://squirrelmail.org/plugin_view.php?id=209

When I compose a new e-mail message, type something into the body, and click ABC to bring up the spell checker, it brings up an empty main texarea box (see attachment), and doesn't display any words at all.

I view the javascript console and see the following errors/warnings:

Error: init_spell is not defined
Source File: http://webmaildomain.com/plugins/html_mail/fckeditor/editor/dialog/fck_spellerpages/spellerpages/server-scripts/spellchecker.php
Line: 1

Error: wordWindowObj is not defined
Source File: http://webmaildomain.com/plugins/html_mail/fckeditor/editor/dialog/fck_spellerpages/spellerpages/server-scripts/spellchecker.php
Line: 42

Error: invalid regular expression flag h
Source File: http://webmaildomain.com/plugins/html_mail/fckeditor/editor/dialog/fck_spellerpages/spellerpages/server-scripts/spellchecker.php
Line: 12,
Column: 64

Source Code:
Warning: Invalid argument supplied for foreach() in <b>/home/username/public_html/plugins/html_mail/fckeditor/editor/dialog/fck_spellerpages/spellerpages/server-scripts/spellchecker.php</b> on line <b>31</b><br />

Error: syntax error
Source File: http://webmaildomain.com/plugins/html_mail/fckeditor/editor/dialog/fck_spellerpages/spellerpages/server-scripts/spellchecker.php
Line: 21, Column: 1
Source Code:
if( error ) {