fix missing database check when doing RL without a given database

[maurerle]

This fixes commands like:

assume -s example_02a -c tiny which did throw: AttributeError: 'NoneType' object has no attribute 'begin' before

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.48%. Comparing base (ef325c0) to head (fe85a55).
Report is 36 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #492   +/-   ##
=======================================
  Coverage   76.47%   76.48%           
=======================================
  Files          49       49           
  Lines        6318     6319    +1     
=======================================
+ Hits         4832     4833    +1     
  Misses       1486     1486           

Flag	Coverage Δ
pytest	76.48% <100.00%> (+<0.01%)	⬆️

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[kim-mskw]

Interesting I'll review it @nick-harder