Adhere to the common coding style of Git and not check explicitly
for NULL throughout the file. There are still other occurrences in the
code base but that is usually inside of conditions with side effects.
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>