erasure coding: fix cases where there are no .ecj files

weed/shell/command_volume_fix_replication.go

@@ -121,7 +121,10 @@ func (c *commandVolumeFixReplication) Do(args []string, commandEnv *CommandEnv,
 						VolumeId:       volumeInfo.Id,
 						SourceDataNode: sourceNode.dataNode.Id,
 					})
-					return fmt.Errorf("copying from %s => %s : %v", sourceNode.dataNode.Id, dst.dataNode.Id, replicateErr)
+					if replicateErr != nil {
+						return fmt.Errorf("copying from %s => %s : %v", sourceNode.dataNode.Id, dst.dataNode.Id, replicateErr)
+					}
+					return nil
 				})
 
 				if err != nil {