don't log errors when all is fine
[ci skip] Format pass of Active Job Basics guide.
Merge pull request #16145 from phoet/patch-2

don't log errors when all is fine
Fixes the digits counter of AS's NumberToRoundedConverter

Zero has one digit, but Math.log10(0) returns -Infinity. The method
needs to special-case zero.

The patch adds a regression test that is not clearly related to the
underlying issue because digit_count is private and has no coverage.
Gray area.

This bug was uncovered by 60062cf.
Merge pull request #16583 from JuanitoFatas/doc/patch-1

[ci skip] Format pass of Active Job Basics guide.