Fix: Arrays of null where data is expected now parses properly

If Struct::autoUpgradeToArray() is enabled, an array of null values would create an arrayOfNULL type in the structure, incompatible with any other array, so no non-null values could appear in such array.

• Example:

  [
    { "runId": [
        null
    ]},
    { "runId": [
        "value"
    ]}
  ]
  

This array would previously fail as incompatible. Now the first is simply ignored.