fixed sfI18N::getDateForCulture raises notices if an invalid date is passed (closes #515)
fixed sfI18N::getDateForCulture raises notices if an invalid date is passed (closes #515)

git-svn-id: 2f0e1b834f829f9d45d4005679b0d62d953a4cdf@1330 4396de85-42e0-4213-a939-0f47b466bcdf

morhekil/symfony,morhekil/symfony,morhekil/symfony