Fix error message

[sirzooro]

Now it would reveal masterKey instead of its length.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.54%. Comparing base (9a71c33) to head (eda7cf1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #376   +/-   ##
=======================================
  Coverage   82.54%   82.54%           
=======================================
  Files          19       19           
  Lines        1472     1472           
=======================================
  Hits         1215     1215           
  Misses        142      142           
  Partials      115      115           

Flag	Coverage Δ
go	82.54% <100.00%> (ø)

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[sirzooro]

Thanks