Closes https://github.com/ppy/osu/issues/25815. `CollectionDropdown.collectionsChanged()` was assuming that if it received `null` changes, then it must mean that the change subscription is being initialised and the `filters` list will not contain any items. However, that is not the only circumstance wherein a realm subscription can fire with `null` changes; that can also happen after the main realm instance gets recycled via the notification registration flow: https://github.com/ppy/osu/blob/2f28a92f0a03c8aed6fac2ec7fb41f7ed865f798/osu.Game/Database/RealmAccess.cs#L545-L549 https://github.com/ppy/osu/blob/2f28a92f0a03c8aed6fac2ec7fb41f7ed865f798/osu.Game/Database/RealmAccess.cs#L1228-L1251 Therefore, to fix the crash, just ensure that the list is cleared every time.
CollectionDropdown
Co-authored-by: Dean Herbert <pe@ppy.sh>
Allows easier targetting when there is a lot of content in the scroll view As discussed in https://github.com/ppy/osu/discussions/24095#discussioncomment-6332398.