Add validations to catch empty train/test scenarios

[gaugup]

Description

Adding these validations to make sure the downstream predict calls don't fail unexpectedly.

Checklist

• I have added screenshots above for all UI changes.
• I have added e2e tests for all UI changes.
• Documentation was updated if it was needed.

[codecov-commenter]

Codecov Report

Merging #1749 (aaf4c97) into main (2050f20) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1749   +/-   ##
=======================================
  Coverage   89.85%   89.85%           
=======================================
  Files          32       32           
  Lines        1626     1626           
=======================================
  Hits         1461     1461           
  Misses        165      165           

Flag	Coverage Δ
unittests	89.85% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/gaugup/AddEmptyDataValidations/dashboard/index.html

[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/gaugup/AddEmptyDataValidations/dashboard/index.html

[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/gaugup/AddEmptyDataValidations/dashboard/index.html