If a matching recipe is not found then return Null instead of raising
KeyError because we were blindly using None as a key for pkg_fn.
(Bitbake rev: 431e89e322850a2497157c3c0843da9df6bc9a3e)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>