Misleading error when sending `_id` as an object in collections mode

[vkarpov15]

Sending the following insertMany command:

{
    "insertMany": {
        "documents": [
            {
                "text": "The Great Train Robbery\n\nA group of bandits stage a brazen train hold-up, only to find a determined posse hot on their heels.\n\nAmong the earliest existing films in American cinema - notable as the first film that presented a narrative story to tell - it depicts a group of cowboy outlaws who hold up a train and rob the passengers. They are then pursued by a Sheriff's posse. Several scenes have color included - all hand tinted.",
                "_id": {
                    "buffer": {
                        "0": 105,
                        "1": 120,
                        "2": 241,
                        "3": 2,
                        "4": 75,
                        "5": 208,
                        "6": 117,
                        "7": 104,
                        "8": 111,
                        "9": 60,
                        "10": 215,
                        "11": 86
                    }
                }
            }
        ],
        "options": {
            "returnDocumentResponses": true,
            "ordered": false
        }
    }
}

gives me the following error:

{"errors":[{"message":"Server failed: root cause: (java.util.NoSuchElementException) No value present","errorCode":"SERVER_UNHANDLED_ERROR","id":"c6ecb197-945b-4e74-9fb5-fb5919e4432d","family":"SERVER","title":"Server failed","scope":"EMPTY"}]}

Similar to #2275, but this one is in collections not tables. The _id is malformed due to a mistake in my code but the error message should indicate something along the lines of an invalid _id not an unhandled error.