Fix NPE when submitting review with inline comments via REST

NPE occurs when submitting a review with inline comments in
the format:

  {
    "comments": {
      "test.txt": [
        {
          "line": 1,
          "message": "comment"
        },
      ]
    }
  }

The comma following the closing brace after the `"message": "comment"`
line seems to be causing an iterator with a null element to be
generated.

NPE does not occur when the comma is omitted.

To prevent the NPE remove the null element from the iterator.

Change-Id: I248739fce955522f7ee4a93441e48914342d3d7d
1 file changed