When removing items, we perform a two-pass removal, checking first
for the cached rectangle collision. Then, if we do not find the item
being removed, we perform a second, more expensive pass over the full
tree. This second pass is required as we cannot be certain that an
item's bbox has not been modified between insertion and deletion. In
which case, keeping stale pointers in the tree will lead to segfaults.
Fixes: lp:1777246
* https://bugs.launchpad.net/kicad/+bug/1777246
4959f91dac