Just wondering, if a Microflow retrieve activity retrieves objects with a constraint such as [MyAssociation = $AnotherObject] and $AnotherObject = empty. Does it throw an exception or does it return all items where MyAssociation is not set?
Figured it out myself, the answer is neither of them:
The result set is just always empty when $AnotherObject does not resolve.
(When MyAssociation is a reference, did not test for references)