Array to string conversion in drupal_validate_utf8() error

Hi. The module works fine. But I get this error:

Notice: Array to string conversion in drupal_validate_utf8() (line 1593 of /home/public_html/includes/bootstrap.inc).
Warning: preg_match() expects parameter 2 to be string, array given in drupal_validate_utf8() (line 1599 of /home/public_html/includes/bootstrap.inc)

I get this error after I add Instagram block to Panel content and save it. Looks like it works all fine, but when editing/going to Panel content edit page where this Instagram Block is included it gives this error in red.