Inconsistency in test case result files

I've noticed an inconsistency in the test case result files that makes
automated testing difficult (at least using a graph equivalence measure).

In some cases, when a solution has an unbound variable, a binding is
included for the variable with no value:

http://www.w3.org/2001/sw/DataAccess/tests/data/examples/ex11.2.3.2_0-result
.n3

In others, no binding is included:

http://www.w3.org/2001/sw/DataAccess/tests/data/Expr1/expr-3-result.ttl


-Geoff