Convert assertIdentical(NULL..) to assertNull(...)

Problem/Motivation

We're working towards replacing assertIdentical with assertSame. assertSame requires the arguments to be ($expected, $actual, ...), whereas assertIdentical requires ($actual, $expected,...).

Proposed resolution

In preparation for the final cleanup, change all assertIdentical calls checking for NULL to assertNull.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet