Kafka event without headers

[cavus700]

Hello,
I am not sure if this is an actual bug or if I miss something in the SDK but in my understanding this should work.

I am receiving a cloud event without any headers from a kafka instance:

------------------ Message -------------------

Topic Name: mytopic

------------------- key ----------------------

Key: mykey

------------------ headers -------------------

------------------- value --------------------

{
    "specversion" : "1.0",
    "type" : "com.example.someevent",
    "source" : "/mycontext/subcontext",
    "id" : "1234-1234-1234",
    "time" : "2018-04-05T03:56:24Z",
    "datacontenttype" : "application/json",
    "data" : {
        ... application data encoded in JSON ...
    }
}

-----------------------------------------------

The problem is that the SDK does not set a format for this message because the format is extracted from the headers here:
https://github.com/cloudevents/sdk-go/blob/main/protocol/kafka_sarama/v2/message.go#L47

This causes an error in the ToEvent() function here:
https://github.com/cloudevents/sdk-go/blob/main/v2/binding/to_event.go#L32

Is there a way to successfully parse an event like this or is this a bug in the SDK? The spec does not require a content-type header for structured events as I can see.