Set preference invisible when no anomaly

In the previous code path, we will create an invisible anomaly preference
and update it to visible if it contains any anomaly. However, when
anomaly is dismissed we don't reset preference to invisible.

So, this cl adds code to set it to invisible explicitly when anomaly list
is empty.

Bug: 64617126
Test: RunSettingsRoboTests
Change-Id: Ie7a3498da91243f05f4c47fb1cc5f67b177d04b1