resolv: use safe navigation operator to avoid extra hash lookups

@addr2name is a private Hash and never changes its default_proc,
so only pay the hash lookup cost once; we know missing entries
in the hash will be nil.

* lib/resolv.rb (each_name): use safe navigation operator

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56890 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/resolv.rb

@@ -264,9 +264,7 @@ class Resolv
 
     def each_name(address, &proc)
       lazy_initialize
-      if @addr2name.include?(address)
-        @addr2name[address].each(&proc)
-      end
+      @addr2name[address]&.each(&proc)
     end
   end