fix issue where passing None as parameter to a query would fail

[thrau]

Motivation

It was pointed out by the platform team, specifically @Pive01 (thank you! 🙏), that #6 introduced a bug, where you could no longer pass None as a parameter value. This created a failure downstream. For example, this is a reasonable way to create a param dict:

parameters = {
   "since": since.isoformat() if since else None
}

This PR adds tests, updates the type hints, and fixes the underlying error. Also bumps the version to 0.5.2

Changes

• None values can now be passed as parameters again to the query and pipes api.