MARC Batch Edit replace functionality

[Angela Kilsdonk]

This was tested in EG 2.1 and 2.2

Replacing more than one subfield in MARC Batch Edit results in an Internal Server Error. For example:
Action: Replace
MARC Tag: 245
Subfields: ac
MARC Data: $aHarry Potter and the philospher’s stone / $cby J.K. Rowling

I am able to successfully replace a single subfield at a time; however, by default, this results in the subfields displaying in the wrong order:
=245 10$cby J.K. Rowling ; illustrations by Mary GrandPré.$aHarry Potter and the philospher's stone

I think it would be desirable to be able to replace multiple subfields at the same time and have the ability to replace a single subfield and maintain the correct order in the MARC record.