Fix wrong array index bound in NotificationUsageStats

Symptom:
It's possible to cause ArrayIndexOutOfBoundsException.

Root cause:
There is an error in the argument check, there is a possibility of
accessing an incorrect Index

Solution:
Fix the argument check correctly

Bug: 36542230

Change-Id: I3dea387c4a2bbddcc68db06812b57fd9d300f778