FIX: Make avatar-flair component fail gracefully group info missing (#13398)

This can happen when an avatar-flair component is rendered to an anonymous user on a login_required site (e.g. when they are redeeming an invite). The lack of group information was causing an error to be raised. With this commit, it now simple skips rendering the flair.

app/assets/javascripts/discourse/app/lib/avatar-flair.js

@@ -52,7 +52,7 @@ function initializeAutoGroupFlair(site) {
     "trust_level_3",
     "trust_level_4",
   ].forEach((groupName) => {
-    const group = site.groups.findBy("name", groupName);
+    const group = site.groups?.findBy("name", groupName);
     if (group && group.flair_url) {
       _noAutoFlair = false;
       _autoGroupFlair[groupName] = {

app/assets/javascripts/discourse/tests/integration/components/user-avatar-flair-test.js

@@ -147,6 +147,26 @@ discourseModule(
       },
     });
 
+    componentTest("avatar flair for login-required site, before login", {
+      template: hbs`{{user-avatar-flair user=args}}`,
+      beforeEach() {
+        resetFlair();
+        this.set("args", {
+          admin: false,
+          moderator: false,
+          trust_level: 3,
+        });
+        // Groups not serialized for anon on login_required
+        this.site.groups = undefined;
+      },
+      afterEach() {
+        resetFlair();
+      },
+      test(assert) {
+        assert.ok(!exists(".avatar-flair"), "it does not render a flair");
+      },
+    });
+
     componentTest("avatar flair for primary group flair", {
       template: hbs`{{user-avatar-flair user=args}}`,
       beforeEach() {