Hi, I had the same problem but this cleared it all up. Found it in this page:
https://www.cambridgewebworks.com/forum/index.php?PHPSESSID=c9349ba5a69f97890537c5f62e04baca&topic=12.new
ENJOY!
We installed the excellent WordPress component for Joomla, but when used together with SEF Advance we get an error on the blog page;
Warning: rawurlencode() expects parameter 1 to be string, array given in /var/www/vhosts/cambridgewebworks.com/httpdocs/components/com_jd-wp/wp-includes/classes.php on line 1609
In order to fix this you need to do the following;
? Find the classes.php file in the ‘wp-include’ folder
? Open it in an HTML editor
? Go to line 1609 which looks like this;
$this->query_string .= $wpvar . ‘=’ .
rawurlencode($this->query_vars[$wpvar]);
? now change it to this;
$this->query_string .= $wpvar . ‘=’ .
rawurlencode($this->query_vars[$wpvar[0]]);
Now the error shown on the blog page will no longer show. Excellent!
em