Add conditional around update hook quiz_update_7524()

Thanks, doesn't hurt though my actual problem looked more related to entity controller being loaded due to that update which complained that the tid didn't exist... but I don't know how to resolve that besides doing a registry rebuild.

WD php: PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'base.tid' in 'field list': SELECT base.qnp_id AS qnp_id, base.vid AS vid, base.nid AS nid, base.uid AS uid, base.number_of_random_questions AS number_of_random_questions, base.max_score_for_random AS max_score_for_random, base.pass_rate AS pass_rate, base.summary_pass AS summary_pass, base.summary_pass_format AS summary_pass_format, base.summary_default AS summary_default,                  [error]
base.summary_default_format AS summary_default_format, base.randomization AS randomization, base.backwards_navigation AS backwards_navigation, base.keep_results AS keep_results, base.repeat_until_correct AS repeat_until_correct, base.quiz_open AS quiz_open, base.quiz_close AS quiz_close, base.takes AS takes, base.show_attempt_stats AS show_attempt_stats, base.time_limit AS time_limit, base.quiz_always AS quiz_always, base.tid AS tid, base.time_left AS time_left,
base.max_score AS max_score, base.allow_skipping AS allow_skipping, base.allow_resume AS allow_resume, base.allow_jumping AS allow_jumping, base.allow_change AS allow_change, base.allow_change_blank AS allow_change_blank, base.build_on_last AS build_on_last, base.show_passed AS show_passed, base.mark_doubtful AS mark_doubtful, base.review_options AS review_options, base.result_type AS result_type
FROM
{quiz_node_properties} base
WHERE  (base.vid IN  (:db_condition_placeholder_0)) ; Array
(
    [:db_condition_placeholder_0] => 245
)
 in EntityAPIController->query() (line 187 of entity/includes/entity.controller.inc).
Drush command terminated abnormally due to an unrecoverable error.                                                                                                                                                                                                                                                                                                                                                                                                                     [error]
PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'base.tid' in 'field list': SELECT base.qnp_id AS qnp_id, base.vid AS vid, base.nid AS nid, base.uid AS uid, base.number_of_random_questions AS number_of_random_questions, base.max_score_for_random AS max_score_for_random, base.pass_rate AS pass_rate, base.summary_pass AS summary_pass, base.summary_pass_format AS summary_pass_format, base.summary_default AS summary_default, base.summary_default_format AS summary_default_format, base.randomization AS randomization, base.backwards_navigation AS backwards_navigation, base.keep_results AS keep_results, base.repeat_until_correct AS repeat_until_correct, base.quiz_open AS quiz_open, base.quiz_close AS quiz_close, base.takes AS takes, base.show_attempt_stats AS show_attempt_stats, base.time_limit AS time_limit, base.quiz_always AS quiz_always, base.tid AS tid, base.time_left AS time_left, base.max_score AS max_score, base.allow_skipping AS allow_skipping, base.allow_resume AS allow_resume, base.allow_jumping AS allow_jumping, base.allow_change AS allow_change, base.allow_change_blank AS allow_change_blank, base.build_on_last AS build_on_last, base.show_passed AS show_passed, base.mark_doubtful AS mark_doubtful, base.review_options AS review_options, base.result_type AS result_type
FROM
{quiz_node_properties} base
WHERE  (base.vid IN  (:db_condition_placeholder_0)) ; Array
(
    [:db_condition_placeholder_0] => 245
)
 in EntityAPIController->query() (line 187 of entity/includes/entity.controller.inc).