The smartlist functions take great care to reset unused pointers inside
the smartlist memory to NULL.
The function smartlist_remove_keeporder does not clear memory in such
way when elements have been removed. Therefore call memset after the
for-loop that removes elements. If no element is removed, it is
effectively a no-op.
Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
