Fix: Submitting ' ' in human mode crashes container

[klieret]

Fixes #748

[codecov]

Codecov Report

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

Project coverage is 74.29%. Comparing base (56816e7) to head (186b89d).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
sweagent/agent/models.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #749   +/-   ##
=======================================
  Coverage   74.29%   74.29%           
=======================================
  Files          27       27           
  Lines        3712     3712           
=======================================
  Hits         2758     2758           
  Misses        954      954           

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