Constant, year/month/day and List multipart idno number elements not set for media in batch importer

Constant, year/month/day and List multipart idno number elements are not set for media when batch imported with auto-generated identifiers and background processing is employed.

For example, if the numbering format is YEAR.Serial #, when imported interactively the identifier will be set to 2018.100 (or the like). With background processing the resulting identifier would be .100.