Consume nil in Unpacker#skip_nil

Co-Authored-By: Jean Boussier <jean.boussier@gmail.com>

Author: OskarEichler

ext/msgpack/unpacker.c

@@ -911,8 +911,8 @@ int msgpack_unpacker_skip_nil(msgpack_unpacker_t* uk)
         return b;
     }
     if(b == 0xc0) {
+        reset_head_byte(uk);
         return 1;
     }
     return 0;
 }
-

spec/cruby/unpacker_spec.rb

@@ -11,8 +11,9 @@
   end
 
   it 'skip_nil succeeds' do
-    unpacker.feed("\xc0")
+    unpacker.feed("\xc0*")
     unpacker.skip_nil.should == true
+    unpacker.unpack.should == 42
   end
 
   it 'skip_nil fails' do