base: Allow unpack to handle localpath=None

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

meta/classes/base.bbclass

@@ -317,6 +317,8 @@ python base_do_unpack() {
 			local = bb.data.expand(bb.fetch.localpath(url, localdata), localdata)
 		except bb.MalformedUrl, e:
 			raise FuncFailed('Unable to generate local path for malformed uri: %s' % e)
+                if local is None:
+                    continue
 		local = os.path.realpath(local)
 		ret = oe_unpack_file(local, localdata, url)
 		if not ret: