[AIRFLOW-5073] Change SQLSensor to optionally treat NULL as keep poking

[uncletoxa]

Fixing bug treating "NULL" as NULL in sql sensor.

Jira

• My PR addresses the following:
  • https://issues.apache.org/jira/browse/AIRFLOW-5073

Description

• Here are some details about my PR, including screenshots of any UI changes:
• fixes bugs from previous PR - [AIRFLOW-5073] Change SQLSensor to keep poking receving NULL, '0' #5913 (comment)

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

Code Quality

• Passes flake8

[uncletoxa]

bump
Looks like CI issues does not belong to my PR

[OmerJog]

@ashb tests were restarted.. It's ok now