fix: code manager to handle data not defined error

[ArslanSaleem]

• Closes NameError: name 'data' is not defined #1045

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 77.79%. Comparing base (09fb29d) to head (d14f37c).

Files	Patch %	Lines
pandasai/helpers/output_validator.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1048      +/-   ##
==========================================
+ Coverage   77.76%   77.79%   +0.02%     
==========================================
  Files         113      113              
  Lines        4313     4318       +5     
==========================================
+ Hits         3354     3359       +5     
  Misses        959      959              

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