Do not create a RemoveAlreadyRemovedTiles unless needed

If the flag is off, we should not create it (as it will fail the
assertion). This passed in presubmit because `assert` does not throw in
regular builds.

Test: gradle build
Fixes: 435705200
Flag: com.android.systemui.reset_tiles_removes_custom_tiles
Change-Id: Ib6005ece4c7f7a7efecfad8e14c413276ae79ed6