Usually, this type of error is produced if stats file is missed, check if aseg. stats file is there in directory "/usr/local/freesurfer/subjects/140/stats" directory.

If this file is missed in some subjects, you can add "--skip" to command line like;

asegstats2table --subjects 01 02 03 .... --meas volume --skip --statsfile wmparc.stats --all-segs --tablefile .......

Jamaan