[PATCH] kobject: don't oops on null kobject.name

kobject_get_path() will oops if one of the component names is
NULL.  Fix that by returning NULL instead of oopsing.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>