fix leak in error handling of debug populate command (#7062)

valsize was not modified during the for loop below instead of getting from c->argv[4], therefore there is no need to put inside the for loop.. Moreover, putting the check outside loop will also avoid memory leaking, decrRefCount(key) should be called in the original code if we put the check in for loop

(cherry picked from commit c69a9b2f61)

src/debug.c

@@ -591,14 +591,13 @@ NULL
         if (getLongFromObjectOrReply(c, c->argv[2], &keys, NULL) != C_OK)
             return;
         dictExpand(c->db->dict,keys);
+        long valsize = 0;
+        if ( c->argc == 5 && getLongFromObjectOrReply(c, c->argv[4], &valsize, NULL) != C_OK ) 
+            return;
         for (j = 0; j < keys; j++) {
-            long valsize = 0;
             snprintf(buf,sizeof(buf),"%s:%lu",
                 (c->argc == 3) ? "key" : (char*)c->argv[3]->ptr, j);
             key = createStringObject(buf,strlen(buf));
-            if (c->argc == 5)
-                if (getLongFromObjectOrReply(c, c->argv[4], &valsize, NULL) != C_OK)
-                    return;
             if (lookupKeyWrite(c->db,key) != NULL) {
                 decrRefCount(key);
                 continue;