Report errors and ensure file exists

[laritakr]

Story

Even though the file is put into the correct path location during the child_work_creation_from_pdf_service, we sometimes were finding that the file did not exist at the point we needed it (when running larger import batches). This change:

• ensures the file exists at the path
• reports if no image_files are found to split into

Expected Behavior Before Changes

Expected Behavior After Changes

Screenshots / Video

Notes