Trigger null-selection in SongSelect when the last beatmap is hidden
This avoids `SelectionChanged` potentially being invoked multiple times after `selectedBeatmapSet` is already `null`.
Fix null reference in release builds
Not sure if we will keep this going forward (there will likely be an opaque tab control on the notifications overlay similar to options) but let's go with this for now.
Intro may not be initialised yet
Fix supporter icon appearing incorrectly in user profile header
add missing line
Results in incorrect default formatting.
also it doesn't show up on profiles without supporter anymore
and minor cleanup
Also better handles delays before notifications are displayed.
still wip tho bleh bleh
Let NotificationOverlay move the background
Fix NotificationOverlay going out of bounds at the bottom