The if statement current causes the size of parent to be calcuated which
is like a len() operation on a datastore. Since we're only interested
whether the value is none, checking explictly for this gives a
small performance gain.
(Bitbake rev: 43a245bde318545ea75ca4ce7894395c1cf9b32a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>