Fix more protocol errors

Former-commit-id: 7fc6d6c6b177ad88dcddd0f4a7f68b74ccdaf037

src/object.cpp

@@ -1373,7 +1373,7 @@ NULL
             }
         }
         if ((de = dictFind(c->db->pdict,ptrFromObj(c->argv[2]))) == NULL) {
-            addReplyNull(c, shared.nullbulk);
+            addReplyNull(c);
             return;
         }
         size_t usage = objectComputeSize((robj*)dictGetVal(de),samples);

src/pubsub.cpp

@@ -89,7 +89,7 @@ void addReplyPubsubUnsubscribed(client *c, robj *channel) {
     if (channel)
         addReplyBulk(c,channel);
     else
-        addReplyNull(c, shared.nullbulk);
+        addReplyNull(c);
     addReplyLongLong(c,clientSubscriptionsCount(c));
 }
 
@@ -117,7 +117,7 @@ void addReplyPubsubPatUnsubscribed(client *c, robj *pattern) {
     if (pattern)
         addReplyBulk(c,pattern);
     else
-        addReplyNull(c, shared.nullbulk);
+        addReplyNull(c);
     addReplyLongLong(c,clientSubscriptionsCount(c));
 }