Error Upon *Second* Use of Heal Selection

[Shabs.lists]

For example: In the attached image, for example, there is a blackish smudge on her left hand. When I try to delete the smudge with Heal Selection, I get the above mentioned errors, namely:
GIMP MESSAGE: Calling error for procedure 'plug-in-resynthesizer':
The texture source is empty. Does any selection include non-transparent pixels?

and

An error occurred running python_fu_heal_selection
RuntimeError: The texture source is empty. Does any selection include non-transparent pixels?