Issue Summary

For CSV import (admin and non-admin), attempting to unset/clear the 'Flagged' field throws an error:

The value [ {null=0} ] can't be added to the Custom Field [ Flagged ]. The value [ {null=0} ] can't be found or is in the incorrect format.

The 'Flagged' field has two supported values: 'Impediment' and blank. The field can be successfully set to 'Impediment', but clearing/unsetting it via values like blank, space, 0, false, False, and FALSE yield the aforementioned error.

Steps to Reproduce

1. Attempt to import a CSV like this sample:

Summary,Flagged
Imported item with Flagged set,TRUE
Imported item with Flagged unset,FALSE

      2. Proceed through the mapping and validation steps

Expected Results

'Flagged' field is unset

Actual Results

The below exception is thrown during validation:

The value [ {null=0} ] can't be added to the Custom Field [ Flagged ]. The value [ {null=0} ] can't be found or is in the incorrect format. 

Workaround

The error shown during validation can be ignored, and the user can proceed with the import. Items that experience this error still import and the 'Flagged' field is unset.