Invalid argument error

I’ve installed but get this error at the top of the page:

“Warning: Invalid argument supplied for foreach() in /wp-content/plugins/spamreferrerblock/spam_referrer_block.php on line 104”

Line 104:
foreach($items as $item => $status) {

Any ideas?

Thanks
Mike

https://www.ads-software.com/plugins/spamreferrerblock/