Without this change, there would be a couple of pixels between each list
item where nothing would be hovered. This is a pretty annoying UX which
we should be avoiding we possible.
Also removes the necessity of scheduling as it actually never worked as
intended, `Scheduler` will still update even when the chat line is
masked away, and the animation will never be held anyways.
The new duration of the animation should be enough for long scrolls
either way.
In the case a message arrives and the chat overlay is hidden, clicking
on the mention notification will not work as the `HighlightedMessage`
bindable callback will execute before the scheduled `newMessagesArrived`
logic (which was hanging since the message arrived until the chat
overlay became open because of the notification).
Simplify things by always scheduling the `HighlightedMessage` bindable
callback.
As seen by this kind of crash, having the `.ToMod` method throw can be
very problematic and also hidden (as it is used inside of models in
places where exceptions are not expected to occur).
Given there are tens of usages of this method, returning a placeholder
mod seems like a better idea than outright throwing.
```
An unhandled has occurred.
System.InvalidOperationException:
There is no mod in the ruleset (osu) matching the acronym AS.
at osu.Game.Online.API.APIMod.ToMod(Ruleset ruleset) in /Users/dean/Projects/osu/osu.Game/Online/API/APIMod.cs:line 54
at osu.Game.Scoring.ScoreInfo.<get_Mods>b__117_0(APIMod m) in /Users/dean/Projects/osu/osu.Game/Scoring/ScoreInfo.cs:line 193
at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
at osu.Game.Scoring.ScoreInfo.get_Mods() in /Users/dean/Projects/osu/osu.Game/Scoring/ScoreInfo.cs:line 193
at osu.Game.Screens.Select.Leaderboards.BeatmapLeaderboard.<>c.<subscribeToLocalScores>b__40_2(ScoreInfo s) in /Users/dean/Projects/osu/osu.Game/Screens/Select/Leaderboards/BeatmapLeaderboard.cs:line 199
at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
at osu.Game.Database.RealmObjectExtensions.Detach[T](IEnumerable`1 items) in /Users/dean/Projects/osu/osu.Game/Database/RealmObjectExtensions.cs:line 180
at osu.Game.Screens.Select.Leaderboards.BeatmapLeaderboard.<>c__DisplayClass40_0.<subscribeToLocalScores>g__localScoresChanged|1(IRealmCollection`1 sender, ChangeSet changes, Exception exception) in /Users/dean/Projects/osu/osu.Game/Screens/Select/Leaderboards/BeatmapLeaderboard.cs:line
209
at Realms.RealmCollectionBase`1.Realms.INotifiable<Realms.NotifiableObjectHandleBase.CollectionChangeSet>.NotifyCallbacks(Nullable`1 changes, Nullable`1 exception)
at Realms.NotifiableObjectHandleBase.NotifyObjectChanged(IntPtr managedHandle, IntPtr changes, IntPtr exception)
```
