In this 3-action flow:
where the compose is
last(split((outputs('Get_attachments')?['body/DisplayName'], '.'))
I get
InvalidTemplate. Unable to process template language expressions in action 'Compose' inputs at line '0' and column '0': 'The template language function 'split' expects its first parameter to be of type string. The provided value is of type 'Null'. Please see https://aka.ms/logicexpressions#split for usage details.'.
Yet very clearly the body of the output contains the string?!?!!?