The NullHandler class in git.util was added when merging gitpython-developers#300, to
allow a noop handler to be used on Python 2.6, since the standard
library logging.NullHandler class was added in Python 2.7.
When introduced in  d1a9a23 , the git.util.NullHandler class was also
patched into the logging module, but that has no longer been done
since  2fced2e  (gitpython-developers#979), nor does GitPython make other use of it.
This also changes the parameter type annotation on the emit method
from `object` to `logging.LogRecord`, which is the expeced type.