BUG on CI 3.1.7 with ION AUTH

After the last update from 3.1.6 to 3.1.7 a problem apperars with register.

Function auth/create_user() has problem on validation around line 561

ERROR Messages 
Message: Use of undefined constant INTL_IDNA_VARIANT_UTS46 - assumed 'INTL_IDNA_VARIANT_UTS46'