Fix parse_url() path error on home page in Rules\ThreeSegmentUrls

The report queue fails as soon as it gets to the home page. This is caused by the missing path index.

Same fix as abd1697 for similar bug #111 .

src/Reporting/Rules/ThreeSegmentUrls.php

@@ -27,7 +27,7 @@ public function siteWarningComment()
 
     public function processPage()
     {
-        $url = parse_url($this->page->url())['path'];
+        $url = parse_url($this->page->url())['path'] ?? '/';
         $this->slashes = substr_count($url, '/');
     }