filer.backup: ignore missing volume/lookup errors when -ignore404Error is set (#7889)

* filer.backup: ignore missing volume/lookup errors when -ignore404Error is set (#7888)

* simplify

weed/command/filer_backup.go

@@ -146,10 +146,17 @@ func doFilerBackup(grpcDialOption grpc.DialOption, backupOption *FilerBackupOpti
 			if err == nil {
 				return nil
 			}
+			// ignore HTTP 404 from remote reads
 			if errors.Is(err, http.ErrNotFound) {
 				glog.V(0).Infof("got 404 error, ignore it: %s", err.Error())
 				return nil
 			}
+			// also ignore missing volume/lookup errors coming from LookupFileId or vid map
+			errStr := err.Error()
+			if strings.Contains(errStr, "LookupFileId") || (strings.Contains(errStr, "volume id") && strings.Contains(errStr, "not found")) {
+				glog.V(0).Infof("got missing-volume error, ignore it: %s", errStr)
+				return nil
+			}
 			return err
 		}
 	} else {