There is a need to support single blobovnicza in blobovnicza tree. This can
be achieved with a width of 1, and a depth of 0 or 1. With depth = 1 one
redundant directory is created, inside which there is a blobovnicza. If the
depth is zero, the blobobnivza will be in the root path. Fix negative
capacity in iterateDeepest method with zero depth.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
