[Expressive design] Update all properties in TopIntroPreference

When some TopIntroPreference's parameters are given as NULL, the
corresponding properties should be also set accordingly, to avoid
leftovers while replacing the item with another with the same
preference key.

Bug: 421362889
Test: visual
Flag: EXEMPT library update

Change-Id: I54ec62cab2edca9a167d77a4a240bd9554083184
Signed-off-by: Stefan Maftei <smaftei@google.com>