Zero Point site down with DrupalChat

Recently I installed DrupalChat. When this module is turned on, all content sites are down with the message below (adm sites are still up working):

Error: [] operator not supported for strings in zeropoint_image() (line 471 of /var/www/html/sites/all/themes/zeropoint/template.php)

Here are a few trying results:

1. If I turn the module off, sites are back to normal;
2. If I switch to other themes, DrupalChat works fine;
3. When I set the DrupalChat's option to integrating with iFlyChat within Zero Point, it seems working fine. But I need the setting of Normal.

Really appreciate if someone could help out.

Regards,