Don't try to use display of detached task to update insets

If insets overrides change on a detached task, it shouldn't
have an effect anyways, so don't try to access the display-content
(which will be null when detached)

Bug: 249151208
Test: atest NexusLauncherTests:com.android.launcher3.ui.TaplTestsLauncher3#testAppIconLaunchFromAllAppsFromHome
Change-Id: I97bbb569f99c4f7bdd7e865c9a8122fc6b49bc79