kv: return error from ResponseKeyIterate with nil response

This commit updates ResponseKeyIterate to reject a nonsensical case.

Epic: None
Release note: None

pkg/kv/kvpb/batch.go

@@ -513,7 +513,7 @@ func (ba *BatchRequest) RefreshSpanIterate(br *BatchResponse, fn func(roachpb.Sp
 		if br != nil {
 			resp = br.Responses[i].GetInner()
 		}
-		if ba.WaitPolicy == lock.WaitPolicy_SkipLocked && CanSkipLocked(req) {
+		if ba.WaitPolicy == lock.WaitPolicy_SkipLocked && CanSkipLocked(req) && resp != nil {
 			if ba.IndexFetchSpec != nil {
 				return errors.AssertionFailedf("unexpectedly IndexFetchSpec is set with SKIP LOCKED wait policy")
 			}
@@ -574,7 +574,7 @@ func ActualSpan(req Request, resp Response) (roachpb.Span, bool) {
 // COL_BATCH_RESPONSE scan format.
 func ResponseKeyIterate(req Request, resp Response, fn func(roachpb.Key)) error {
 	if resp == nil {
-		return nil
+		return errors.Errorf("cannot iterate over response keys of %s request with nil response", req.Method())
 	}
 	switch v := resp.(type) {
 	case *GetResponse:

pkg/kv/kvpb/batch_test.go

@@ -413,6 +413,12 @@ func TestResponseKeyIterate(t *testing.T) {
 			resp:    &GetResponse{Value: &roachpb.Value{}},
 			expKeys: []roachpb.Key{keyA},
 		},
+		{
+			name:   "get, no response",
+			req:    &GetRequest{RequestHeader: pointHeader},
+			resp:   nil,
+			expErr: "cannot iterate over response keys of Get request with nil response",
+		},
 		{
 			name:    "scan, missing",
 			req:     &ScanRequest{RequestHeader: rangeHeader, ScanFormat: KEY_VALUES},

pkg/kv/kvserver/replica_tscache.go

@@ -127,7 +127,7 @@ func (r *Replica) updateTimestampCache(
 		header := req.Header()
 		start, end := header.Key, header.EndKey
 
-		if ba.WaitPolicy == lock.WaitPolicy_SkipLocked && kvpb.CanSkipLocked(req) {
+		if ba.WaitPolicy == lock.WaitPolicy_SkipLocked && kvpb.CanSkipLocked(req) && resp != nil {
 			if ba.IndexFetchSpec != nil {
 				log.Errorf(ctx, "%v", errors.AssertionFailedf("unexpectedly IndexFetchSpec is set with SKIP LOCKED wait policy"))
 			}