compiler: Hotfix estimate memory again

[EdCaunt]

@JDBetteridge spotted a bug in estimate_memory, so fixing it here

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.11%. Comparing base (767950b) to head (70c6841).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2707   +/-   ##
=======================================
  Coverage   92.11%   92.11%           
=======================================
  Files         248      248           
  Lines       49640    49640           
  Branches     4367     4367           
=======================================
  Hits        45726    45726           
  Misses       3207     3207           
  Partials      707      707           

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	71.07% <100.00%> (ø)
pytest-gpu-nvc-nvidiaX	72.03% <100.00%> (-0.02%)	⬇️

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