Timeline: repair oldest/newest metrics if we fetch nothing

ts/test-node/util/isMuted_test.ts

@@ -0,0 +1,22 @@
+// Copyright 2020 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isMuted } from '../../util/isMuted';
+
+describe('isMuted', () => {
+  it('returns false if passed undefined', () => {
+    assert.isFalse(isMuted(undefined));
+  });
+
+  it('returns false if passed a date in the past', () => {
+    assert.isFalse(isMuted(0));
+    assert.isFalse(isMuted(Date.now() - 123));
+  });
+
+  it('returns false if passed a date in the future', () => {
+    assert.isTrue(isMuted(Date.now() + 123));
+    assert.isTrue(isMuted(Date.now() + 123456));
+  });
+});