NOTE: Use any section to test (I prefer {nav In-Commerce > Manufacturers}).
# identify 2 fields to be used in test:
* null one with null default value
* not_null one with empty string as default value
Part 1
# create new record with both fields filled-in > confirm that data is stored in db as-is
# edit record and remove value from both fields > confirm that data is stored in db as-is (before NULL was stored in null field instead of empty string)
Part 2
# change default field for both fields to non-empty string
# create record without changing default value of these fields > confirm that data is stored in db as-is
# edit record and remove value from both fields > confirm that data is stored in db as-is (before not null field would revert to default non-empty value)
# create record and immediately clear both fields > confirm that data is stored in db as-is (before not null field would revert to default non-empty value)