message_list: Fix just_unsubscribed for empty views.

This fixes a bug where wrong bookend is shown in empty views in
the next commit.

web/src/message_list.ts

@@ -469,7 +469,7 @@ export class MessageList {
         const is_web_public = sub?.is_web_public;
         if (sub === undefined || sub.is_archived) {
             deactivated = true;
-        } else if (!subscribed && !this.last_message_historical) {
+        } else if (!subscribed && !this.last_message_historical && !this.empty()) {
             just_unsubscribed = true;
         }
 

web/tests/message_list.test.cjs

@@ -387,6 +387,29 @@ run_test("bookend", ({override}) => {
     list.last_message_historical = false;
     is_subscribed = false;
 
+    {
+        const stub = make_stub();
+        list.view.render_trailing_bookend = stub.f;
+        list.update_trailing_bookend();
+        assert.equal(stub.num_calls, 1);
+        const bookend = stub.get_args(
+            "stream_id",
+            "stream_name",
+            "subscribed",
+            "deactivated",
+            "just_unsubscribed",
+        );
+        assert.equal(bookend.stream_id, 5);
+        assert.equal(bookend.stream_name, "IceCream");
+        assert.equal(bookend.subscribed, false);
+        assert.equal(bookend.deactivated, false);
+        assert.equal(bookend.just_unsubscribed, false);
+    }
+
+    list.last_message_historical = false;
+    is_subscribed = false;
+    list.empty = () => false;
+
     {
         const stub = make_stub();
         list.view.render_trailing_bookend = stub.f;