[BUGFIX] [batch.py] fix check for null value (#2994)
[BUGFIX] [batch.py] fix check for null value (#2994)

* [BUGFIX] fix check for null value

* use-isinstance

* fix

* precommit

* syntax tweak

Co-authored-by: James Campbell <1f5d57c840f6bc62c607eb3983b0ef428cfb4438@gmail.com>

Co-authored-by: James Campbell <1f5d57c840f6bc62c607eb3983b0ef428cfb4438@gmail.com>
great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations