Correct child and orphan block removal logic.

It is not safe to remove elements from a slice while iterating them with
the range statement since it does not reevaluate the slice on each
iteration nor does it adjust the index for the modified slice.  This
commit modifies the code to use a for loop with an index (which does
reevaluate on every iteration) and manually adjusts the index when
elements are removed from the slice.