revert changes for processing nulls

go/cmd/dolt/commands/tblcmds/import.go

@@ -761,13 +761,6 @@ func NameAndTypeTransform(row sql.Row, rowOperationSchema sql.PrimaryKeySchema,
 	row = applyMapperToRow(row, rowOperationSchema, rdSchema, nameMapper)
 
 	for i, col := range rowOperationSchema.Schema {
-		if s, ok := row[i].(string); ok {
-			if strings.ToLower(s) == "null" {
-				row[i] = nil
-				continue
-			}
-		}
-
 		// Check if this a string that can be converted to a boolean
 		val, ok := detectAndConvertToBoolean(row[i], col.Type)
 		if ok {

integration-tests/bats/import-create-tables.bats

@@ -813,10 +813,10 @@ DELIM
     [ "${lines[1]}" = "nothing to commit, working tree clean" ]
 }
 
-@test "import-create-tables: import null foreign key value" {
+@test "import-create-tables: import null foreign key value does not violate constraint" {
     cat <<DELIM > test.csv
 id, state_id, data
-1, NULL,poop
+1, ,poop
 DELIM
 
     dolt sql <<SQL