Fix obviously broken error handling.

service/rawdatastore/checkfilter.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package rawdatastore
 
 import (
         "fmt"
 
         "github.com/luci/gae/service/info"
@@ skipping 52 matching lines @@
         for i, k := range keys {
                 if KeyIncomplete(k) {
                         k = NewKey(k.AppID(), k.Namespace(), k.Kind(), "", 1, k.Parent())
                 }
                 if !KeyValid(k, false, tcf.aid, tcf.ns) {
                         lme.Assign(i, ErrInvalidKey)
                         continue
                 }
                 v := vals[i]
                 if v == nil {
-                        if !lme.Assign(i, errors.New("rawdatastore: PutMulti got nil vals entry")) {
-                                lme.Assign(i, v.Problem())
-                        }
+                        lme.Assign(i, errors.New("rawdatastore: PutMulti got nil vals entry"))
+                } else {
+                        lme.Assign(i, v.Problem())
                 }
         }
         if me := lme.Get(); me != nil {
                 for _, err := range me.(errors.MultiError) {
                         cb(nil, err)
                 }
                 return nil
         }
 
         err := error(nil)
@@ skipping 28 matching lines @@
                 }
                 return nil
         }
         return tcf.Interface.DeleteMulti(keys, cb)
 }
 
 func applyCheckFilter(c context.Context, i Interface) Interface {
         inf := info.Get(c)
         return &checkFilter{i, inf.AppID(), inf.GetNamespace()}
 }