DM-46689: Check for list index before comparing to previous in pipetask report cli

[eigerx]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.38%. Comparing base (8a8e908) to head (22702c2).

Files with missing lines	Patch %	Lines
python/lsst/ctrl/mpexec/cli/script/report.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #310      +/-   ##
==========================================
- Coverage   89.40%   89.38%   -0.03%     
==========================================
  Files          50       50              
  Lines        4427     4427              
  Branches      718      679      -39     
==========================================
- Hits         3958     3957       -1     
  Misses        336      336              
- Partials      133      134       +1     

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[villarrealas]

lgtm