segfault when processing event files

```
> etl_transform(retro, season = 1990)

cd /home/bbaumer/dumps/retro/load; cwgame -n -f 0-83 -y 1990 1990*.EV* > games_1990.csv

Chadwick expanded game descriptor, version 0.7.0
Type 'cwgame -h' for help.
Copyright (c) 2002-2017
Dr T L Turocy, Chadwick Baseball Bureau (ted.turocy@gmail.com)
This is free software, subject to the terms of the GNU GPL license.

[Processing file 1990ATL.EVN.]
[Processing file 1990BAL.EVA.]
[Processing file 1990BOS.EVA.]
[Processing file 1990CAL.EVA.]
[Processing file 1990CHA.EVA.]
[Processing file 1990CHN.EVN.]
[Processing file 1990CIN.EVN.]
[Processing file 1990CLE.EVA.]
[Processing file 1990DET.EVA.]
[Processing file 1990HOU.EVN.]
[Processing file 1990KCA.EVA.]
[Processing file 1990LAN.EVN.]
[Processing file 1990MIL.EVA.]
[Processing file 1990MIN.EVA.]
[Processing file 1990MON.EVN.]
[Processing file 1990NYA.EVA.]
[Processing file 1990NYN.EVN.]
[Processing file 1990OAK.EVA.]
[Processing file 1990PHI.EVN.]
[Processing file 1990PIT.EVN.]
[Processing file 1990SDN.EVN.]
[Processing file 1990SEA.EVA.]
[Processing file 1990SFN.EVN.]
[Processing file 1990SLN.EVN.]
[Processing file 1990TEX.EVA.]
[Processing file 1990TOR.EVA.]

cd /home/bbaumer/dumps/retro/load; cwevent -n -f 0-96 -x 0-60 -y 1990 1990*.EV* > events_1990.csv

Chadwick expanded event descriptor, version 0.7.0
Type 'cwevent -h' for help.
Copyright (c) 2002-2017
Dr T L Turocy, Chadwick Baseball Bureau (ted.turocy@gmail.com)
This is free software, subject to the terms of the GNU GPL license.

[Processing file 1990ATL.EVN.]
Segmentation fault (core dumped)
```

Why? The same command works in a terminal.

No source file or test is named. Start by reproducing etl_transform(retro, season = 1990) and the cwevent command on the listed 1990 event files, then compare the terminal and ETL execution environments. Done means the cause of the segmentation fault is identified and event processing completes consistently in both contexts.

Written by the indexing model from the issue text.