Missing bundle property

I get this fatal error message when adding an image to a promotion referenced to a node using panels_reference_formatter for the media field in the promotion with a mini panel as formatter.

EntityMalformedException: Missing bundle property on entity of type file. in entity_extract_ids() (line 7389 of /includes/common.inc).

ddebug_backtrace() pointed towards Panels Reference Formatter and when we returned (checked out) commit c4f89804c870aff13e26cd7489e51c1fda85f0ce it all worked again.