Revert "Don't implicitly cast NULL to a bool"

This reverts commit 734b384dba2c6c7d2c16e78e0babb383e5f2200a.

Change-Id: Iac1d86c9bb11816a981e8849c9b0d3a95d264412
Merge "Revert "Don't implicitly cast NULL to a bool"" into kitkat