Singleton nodes detected in parsed courses.

During the investigation of all the courses, some courses were found to have singleton boolean logic nodes. An example is CYBR372, with the JSON below.

{
    "_id": "6510c556e07a31d20015914a",
    "name": "CYBR372",
    "crn": [
      32078
    ],
    "title": "Applications of Cryptography",
    "description": "Cryptographic mechanisms are widely deployed for communication and data protection. This course addresses how cryptographic mechanisms can be effectively used within larger security systems and how cryptographic mechanisms can be vulnerable in deployed systems. Topics covered include cryptographic primitives, cryptographic protocols, cryptanalytic techniques on primitives and protocols in deployed systems and attacks based upon common errors in use of libraries. Practical work will include best practice use of cryptographic libraries and attacks.",
    "trimesters": [
      2,
      3
    ],
    "credits": 15,
    "level": 300,
    "prerequisites": [
      {
        "type": "AND",
        "expressions": [
          {
            "type": "OR",
            "expressions": [
              "CYBR171"
            ]
          },
          {
            "type": "OR",
            "expressions": [
              "CYBR271",
              "COMP261"
            ]
          },
          {
            "type": "OR",
            "expressions": [
              "NWEN243"
            ]
          }
        ]
      }
    ]
  },