SINTER/SINTERSTORE/SLEMENTS fix: misisng keys are now not errors, but just like empty sets

TODO

@@ -1,5 +1,6 @@
 BEFORE REDIS 1.0.0-rc1
 
+- Fix INCRBY argument that is limited to 32bit int.
 - Add a new field as INFO output: bgsaveinprogress
 - Remove max number of args limit
 - GETSET

redis.c

@@ -2826,7 +2826,12 @@ static void sinterGenericCommand(redisClient *c, robj **setskeys, int setsnum, r
                     lookupKeyRead(c->db,setskeys[j]);
         if (!setobj) {
             zfree(dv);
-            addReply(c,shared.nokeyerr);
+            if (dstkey) {
+                deleteKey(c->db,dstkey);
+                addReply(c,shared.ok);
+            } else {
+                addReply(c,shared.nullmultibulk);
+            }
             return;
         }
         if (setobj->type != REDIS_SET) {