phutil_nonempty_string() is too strict for branch names, as there seem to be
cases that an integer value is passed. Thus us phutil_nonempty_scalar() instead.
EXCEPTION: (InvalidArgumentException) Call to phutil_nonempty_string() expected null or a string, got: int. at [<arcanist>/src/utils/utils.php:2124] arcanist(), ava(), phorge(), translations(), wmf-ext-misc() #0 <#2> phutil_nonempty_string(integer) called at [<phorge>/src/applications/repository/storage/PhabricatorRepository.php:749]
Closes T15640