IndexError in initials_list() when a *_list attribute contains a doubled-space element #232

first_list/middle_list/last_list are plain public attributes (not properties), so they can be assigned directly, bypassing parse_pieces's whitespace normalization. If an assigned element contains an internal double space, _process_initial (parser.py:269, initials.append(part[0])) crashes with IndexError: string index out of range, because "".split(" ") yields an empty string for the collapsed gap.

Repro:

from nameparser import HumanName
n = HumanName(first='John')
n.middle_list = ['Q  R']   # double space inside one list element
n.initials_list()          # IndexError: string index out of range

Going through the normal constructor/property paths is safe (HumanName("John Q Doe") or first="A B") since those go through parse_pieces, which normalizes whitespace. The crash only happens via direct assignment to the *_list attributes.

Found while reviewing #229 / PR #231 — unrelated to that cleanup; it's a pre-existing issue.