Consistently set outlen to zero for all error paths

[torben-hansen]

Description of changes:

Helps accuracy for certain fuzzing techniques.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.22%. Comparing base (17650cc) to head (abc79da).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3104   +/-   ##
=======================================
  Coverage   78.22%   78.22%           
=======================================
  Files         689      689           
  Lines      122089   122088    -1     
  Branches    17031    17030    -1     
=======================================
  Hits        95501    95501           
+ Misses      25682    25680    -2     
- Partials      906      907    +1     

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