return nil if no need to do anything

weed/shell/command_volume_fix_replication.go

@@ -97,7 +97,7 @@ func (c *commandVolumeFixReplication) Do(args []string, commandEnv *CommandEnv,
 	}
 
 	if len(underReplicatedVolumeIds) == 0 {
-		return fmt.Errorf("no under replicated volumes")
+		return nil
 	}
 
 	if len(allLocations) == 0 {