Reported [on reddit of all
places](https://www.reddit.com/r/osugame/comments/1qhnfdn/every_time_i_make_an_adjustment_to_the_hitcircle/).
The reason that this is happening is as follows:
- Changing a combo colour raises `BeatmapSkinChanged`
- `BeatmapSkinChanged` getting raised triggers the sample chooser
dropdown to repopulate its items (as intended and correctly)
- Setting items of a dropdown can also change its `Current.Value`,
because the relevant logic attempts to ensure that `Current.Value` is
valid in line with the new items
- Therefore the `Current.Value` of the dropdown changes from `null` to
sample set `-1` which corresponds to the "Add new..." item as it's the
only item in the dropdown...
- which is indistinguishable from the sequence of events that happens if
the user manually opens the dropdown and clicks the "Add new..." item.
This change sidesteps this entire car crash by just ensuring that even
beatmaps without custom samples have at least set number 1 initialised
(even if it's empty and has no samples). This means that the initial
value of the dropdown is never `null`, and that every time that the
value changes to the set `-1` it actually is due to user action.
Should have known better than to play these dumb games.
Among others, this features a scary-looking change wherein
`WorkingBeatmap` now exposes a `RealmAccess` via
`IStorageResourceProvider`. This is necessary to make
`RealmBackedResourceStore` actually start firing callbacks when the
edited beatmap's skin is modified by adding new samples to it.