[Plugin: Search Unleashed] Function Implode

Im trying to figure out why search unleashed gives the following error when I click on one of the categories on my website.

Warning: implode() [function.implode]: Invalid arguments passed in /home/bigboss/public_html/wp-content/plugins/search-unleashed/engines/default.php on line 143

Warning: implode() [function.implode]: Invalid arguments passed in /home/bigboss/public_html/wp-content/plugins/search-unleashed/engines/default.php on line 143

It does say it two times, it was not a mistype. I went into the php file and it says the following on line 143

$this->terms = implode( ‘ ‘, $this->terms );

I just don’t know what’s wrong with that line. My website is https://www.triplecz.com, I hope someone can find out whats going on here as I would love to continue using this great plugin.