error conformance + fixes to problems found in fuzz testing

[biojppm]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 85.90308% with 32 lines in your changes missing coverage. Please review.

Project coverage is 97.24%. Comparing base (95866e8) to head (ae1a1b1).
Report is 54 commits behind head on master.

Files with missing lines	Patch %	Lines
src/c4/yml/parse_engine.def.hpp	89.28%	12 Missing ⚠️
src/c4/yml/emit.def.hpp	50.00%	7 Missing ⚠️
src/c4/yml/event_handler_tree.hpp	88.88%	6 Missing ⚠️
tools/parse_emit.cpp	60.00%	4 Missing ⚠️
src/c4/yml/emit.hpp	75.00%	1 Missing ⚠️
src/c4/yml/parse_engine.hpp	0.00%	1 Missing ⚠️
tools/yaml_events.cpp	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #433      +/-   ##
==========================================
- Coverage   97.41%   97.24%   -0.18%     
==========================================
  Files          33       33              
  Lines       11118    11239     +121     
==========================================
+ Hits        10831    10929      +98     
- Misses        287      310      +23     

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