Revert "FIX: reverts #18e2816 (#7940)"

This reverts commit c7b146cbdfda41494c350a58982d2fe54893d2c1.

test/javascripts/acceptance/topic-test.js.es6

@@ -255,6 +255,13 @@ QUnit.test("selecting posts", async assert => {
     exists(".select-all"),
     "it should allow users to select all the posts"
   );
+
+  await click(".toggle-admin-menu");
+
+  assert.ok(
+    exists(".selected-posts.hidden"),
+    "it should hide the multi select menu"
+  );
 });
 
 QUnit.test("select below", async assert => {