User search with 4 letters causes internal server error

[mshabunin]

3 and 5 letters work well. Reproduced in 0.10.2 (via pip) and 0.7.58: https://askbot.org/en/users/?t=user&query=asdf&search= Stacktrace (0.10.2):

Internal Server Error: /users/
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python2.7/site-packages/askbot/views/users.py", line 209, in show_users
    matching_users = models.get_users_by_text_query(search_query, users)
  File "/usr/local/lib/python2.7/site-packages/askbot/models/__init__.py", line 131, in get_users_by_text_query
    return postgresql.run_user_search(users_query_set, search_query)
  File "/usr/local/lib/python2.7/site-packages/askbot/search/postgresql/__init__.py", line 103, in run_thread_search
    return run_full_text_search(query_set, query, 'text_search_vector');
  File "/usr/local/lib/python2.7/site-packages/askbot/search/postgresql/__init__.py", line 96, in run_full_text_search
    models.Q(posts__text__icontains = search_query)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/query.py", line 679, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/query.py", line 697, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1310, in add_q
    clause, require_inner = self._add_q(where_part, self.used_aliases)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1332, in _add_q
    current_negated, allow_joins, split_subq)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1338, in _add_q
    allow_joins=allow_joins, split_subq=split_subq,
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1150, in build_filter
    lookups, parts, reffed_expression = self.solve_lookup_type(arg)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1036, in solve_lookup_type
    _, field, _, lookup_parts = self.names_to_path(lookup_splitted, self.get_meta())
  File "/usr/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1397, in names_to_path
    "Choices are: %s" % (name, ", ".join(available)))
FieldError: Cannot resolve keyword 'title' into field. Choices are: _message_set, activity, activityauditstatus, anonymousanswer, anonymousquestion, askbot_profile, askbot_votes, avatar, award_user, badges, bulktagsubscription, created_tags, date_joined, deleted_posts, deleted_tags, draft_answers, draftquestion, email, endorsed_posts, first_name, followed_threads, followrecord, group_membership, group_messaging_sent_messages, groups, id, incoming_activity, is_active, is_staff, is_superuser, last_edited_posts, last_login, last_name, lastvisittime, localized_askbot_profiles, locked_posts, logentry, messagememo, notification_subscriptions, password, postflagreason, postrevision, postrevisions, posts, question_views, replyaddress, repute, senderlist, suggested_tags, tag_selections, tag_synonyms, thread, unreadinboxcounter, unused_favorite_threads, unused_last_active_in_threads, user_favorite_questions, user_permissions, userassociation, username, userpasswordqueue