[openCypher tck case] match on null

[czpmango]

Unsupported.

  Scenario: [3] `relationships()` on null path
    Given any graph
    When executing query:
      """
      WITH null AS a
      OPTIONAL MATCH p = (a)-[r]->()
      RETURN relationships(p), relationships(null)
      """
    Then the result should be, in any order:
      | relationships(p) | relationships(null) |
      | null             | null                |
    And no side effects