fix: a page whose origin has no host is never told an address by accountsChanged (closes #564)

The background judges each tab by its URL's origin, the only one it can see, so a page its server sandboxes, whose own origin is null, was still sent the new active address on an address switch although all its requests are refused.

The background now names the origin it judged by on each accountsChanged event, and the content script passes the address to the page only when the page's own window.origin is that origin, an empty list otherwise. An event naming no origin also reaches the page as an empty list. chainChanged is unchanged. The README's SiteApproval section says the same.

Judgement call: covered by a unit test that sets window.origin; no browser-suite test.

Model: opus-5-5

src/content/index.js

@@ -49,14 +49,23 @@ window.addEventListener("message", (event) => {
 
 // Listen for events pushed from the background (e.g. accountsChanged)
 runtimeApi().onMessage.addListener((msg) => {
-    if (msg.type === "AUTISTMASK_EVENT") {
-        window.postMessage(
-            {
-                type: "AUTISTMASK_EVENT",
-                eventName: msg.eventName,
-                data: msg.data,
-            },
-            "*",
-        );
+    if (msg.type !== "AUTISTMASK_EVENT") return;
+    // The background chooses the addresses in accountsChanged for the site
+    // at the origin the event names, which is the origin of the tab's URL.
+    // This page hears them only when its own origin is that one. A page whose
+    // origin has no host is not a site: one its server sandboxes with a
+    // Content-Security-Policy has the origin "null" whatever its URL, and is
+    // told no address, as its requests are refused.
+    let data = msg.data;
+    if (msg.eventName === "accountsChanged" && msg.origin !== window.origin) {
+        data = [];
     }
+    window.postMessage(
+        {
+            type: "AUTISTMASK_EVENT",
+            eventName: msg.eventName,
+            data,
+        },
+        "*",
+    );
 });