test_socket.rb: ignore interface without address

* test/socket/test_socket.rb (test_udp_server): ignore interface
  with no address assigned.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46204 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/socket/test_socket.rb

@@ -329,6 +329,7 @@ class TestSocket < Test::Unit::TestCase
       nd6 = {}
       ifaddrs.reject! {|ifa|
         ai = ifa.addr
+        next true unless ai
         s = famlies[ai.afamily]
         next true unless s
         next true if ai.ipv6_linklocal? # IPv6 link-local address is too troublesome in this test.