Fix: error when user balance is zero and no remaining executions to r…

[olethanh]

…emove

[codecov]

Codecov Report

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

Project coverage is 61.51%. Comparing base (15e70e7) to head (91cf787).

Files	Patch %	Lines
src/aleph/vm/orchestrator/tasks.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #661   +/-   ##
=======================================
  Coverage   61.51%   61.51%           
=======================================
  Files          68       68           
  Lines        5986     5986           
  Branches      633      633           
=======================================
  Hits         3682     3682           
  Misses       2149     2149           
  Partials      155      155           

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