Catch when no keys

[ahuang11]

When user has no keys in their environment, provider is None, and it'll error.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 58.40%. Comparing base (6b48e35) to head (37d7b69).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lumen/command/ai.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #933      +/-   ##
==========================================
- Coverage   58.41%   58.40%   -0.01%     
==========================================
  Files         109      109              
  Lines       13900    13902       +2     
==========================================
  Hits         8120     8120              
- Misses       5780     5782       +2     

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