:bug: Improve error handling due to missing parent_work_identifier_property_name value

[laritakr]

Story

The derivative rodeo service defines a class attribute:
class_attribute :parent_work_identifier_property_name, default: 'aark_id'

This attribute is not required, and absence of the metadata causes an error TypeError: no implicit conversion of nil into String in IiifPrint::Jobs::ChildWorksFromPdfJob

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Testing Instructions and Sample Files

Notes

[laritakr]

@jeremyf is there any way to QA this or should it be closed as done?