Db/Sql/Predicate/Expression: Fix method argument handling

* Fix method argument handling of Predicate/Expression to allow single non-scalar values (e.g. null, Predicate instances) as only parameter
* Fix typo in Predicate/Predicate
Test is replaced with `testCanPassSingleZeroParameterValueToConstructor()`.
The `0` part is the important, tested one, where `'foo.bar > ?'` is actually irrelevant for this test.