return empty response if not found

weed/server/filer_grpc_server.go

@@ -19,6 +19,9 @@ import (
 func (fs *FilerServer) LookupDirectoryEntry(ctx context.Context, req *filer_pb.LookupDirectoryEntryRequest) (*filer_pb.LookupDirectoryEntryResponse, error) {
 
 	entry, err := fs.filer.FindEntry(ctx, filer2.FullPath(filepath.ToSlash(filepath.Join(req.Directory, req.Name))))
+	if err == filer2.ErrNotFound {
+		return &filer_pb.LookupDirectoryEntryResponse{}, nil
+	}
 	if err != nil {
 		glog.V(3).Infof("LookupDirectoryEntry %s: %+v, ", filepath.Join(req.Directory, req.Name), err)
 		return nil, err