overview: fix TypeError when displaying empty state

This error occurs when opening Epiphany with no saved history.

Fixes #1914

Part-of: <https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/1228>


(cherry picked from commit 8891a9b26a8c9e1b5cf7af118bfdf7b3ba09e442)

embed/web-process-extension/resources/js/overview.js

@@ -29,6 +29,9 @@ Ephy.Overview = class Overview
     _initialize()
     {
         const anchors = document.getElementsByTagName('a');
+        if (anchors.length === 0)
+            return;
+
         for (let i = 0; i < anchors.length; i++) {
             const anchor = anchors[i];
             if (anchor.className !== 'overview-item')