Created media thumbnails are missing a filename and filemime property

Normally in the preCreate method from the file entity class the filename and mimetype is calculated based on the uri. In cloudconvert_media_thumbnail the uri is set after the create, thus the filename and mimetype is not automatically set. Thus saving the file entity results in a NULL value for filename and filemime property.

The issue it gives is that Internet Explorer will not show the images becaue the headers are incorrect because of the missing mimetype.