message: support collapsed items
diff: @@ -81,7 +81,10 @@ class RoomDistributor {
  // this would happen if the cursor goes beyond the min-height
  while (item) {
  // TODO: collapsed
  - if (size <= MIN_SIZE) {
  + if (this._isCollapsed(item)) {
  + item = item.previous();
  + }
  + else if (size <= MIN_SIZE) {
  item.setSize(MIN_SIZE);
  const remainder = MIN_SIZE - size;
  item = item.previous();
  