RLR Spec Passes null to a Method that Asserts notNull

See Sonar report (click on "new bug").

Given that we coerce an empty string to null, we'd get a misleading message downstream about null not being allowed.

Perhaps add an assert on line 135:

Assert.hasText(expression, "'expression' cannot be null or empty");

however, see the method at line 124 which explicitly passes null (and there are no test cases for that method).