Exported content objects with embedded images in xhtml datatypes are missing their dependant image objects.

Steps to reproduce

Go to Packages -> Content Object Export.
Export a content object with an xhtml datatype containing an embedded image. Make sure option to keep related objects is on ('Keep all in selected nodes').
Check the contents of the .ezpkg file - it should contain an image, but no image is included and so when the object is imported the embedded image is missing.