Make return type consistent
Make return type consistent

Notification count should return 0 if user has no enabled notification type

Change-Id: Ice8f524349a3b760c00aeac64c3a47ba5ecec8db

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo