Remove empty container in siebel message while importing csv file

We are on Siebel version IP23.4. We have a custom WF where we import a CSV file (based on IO to update existing fields in Siebel). Sometime we need to pass blank value under some of the csv header (can be any, not fixed field) as the value doesn't have to be updated (need to retain existing value), but unfortunately the fields gets updated to blank.

The process which we follow is that we first read the csv file using EAI File Transport, then use Read CSV File bs to convert it into Siebel message and finally use upsert of EAI Siebel Adapter to update Siebel.