Allow for failure of media component derivative creation

[barbarahui]

@amywieliczka As we discussed, the updates in this PR set the media component to havemimetype=None and path=None by default. We then check to see if the component path is set, and don't set record['media'] on the record unless it is. This essentially restores the old behavior of the content harvester.

I think that if we instead added the incomplete media field to the index, e.g.:

"media": {
    'mimetype': None,
    'path': None,
    'format': "image"
}

then this would get through to the hosted-simple-image template in the frontend based on the fact that it's a hosted image. Then this line would cause an error because item.contentFile.titleSources was empty:

https://github.com/ucldc/public_interface/blob/main/calisphere/templates/calisphere/objectViewer/hosted-simple-image.html#L33

Or maybe this line would error before that:

https://github.com/ucldc/public_interface/blob/main/calisphere/record.py#L14