Do not rely on `getTaskViewCount` to iterate TaskViews

Using `getChildCount` to iterate TaskViews instead of
`getTaskViewCount` when indices are used. As it is not safe to assume
the TaskView starts from index 0.

Flag: EXEMPT as no functionality changes
Bug: 379942019
Test: Manual
Change-Id: I599b5117f0848e429ebf83fc4b85451e52b4bcab
1 file changed