入力が無い場合にも PREF_CHECK がエラー判定となってしまうのを修正

[nanasess]

Fixes #744

PREF_CHECK の挙動が変わるが、 PREF_CHECK は以下でのみ使用されており、 EXIST_CHECK と併用されているため問題ないと思われる

ec-cube2/data/class/helper/SC_Helper_Customer.php

Line 404 in 4d7ff5b

$objFormParam->addParam('都道府県', $prefix.'pref', INT_LEN, 'n', ['PREF_CHECK', 'EXIST_CHECK', 'NUM_CHECK']);

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.61%. Comparing base (1a66910) to head (9e46652).
Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1113   +/-   ##
=======================================
  Coverage   50.60%   50.61%           
=======================================
  Files          80       80           
  Lines       10258    10260    +2     
=======================================
+ Hits         5191     5193    +2     
  Misses       5067     5067           

Flag	Coverage Δ
tests	50.61% <100.00%> (+<0.01%)	⬆️

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