Fix invalid character reference parsing

[andersk]

https://html.spec.whatwg.org/multipage/parsing.html#character-reference-code

• Fixes #310.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.51%. Comparing base (24e6b2f) to head (fd54d13). Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #429      +/-   ##
==========================================
+ Coverage   97.42%   97.51%   +0.08%     
==========================================
  Files          11       11              
  Lines        1164     1165       +1     
==========================================
+ Hits         1134     1136       +2     
+ Misses         30       29       -1     

Flag	Coverage Δ
unittests-3.10	97.51% <100.00%> (+0.08%)	:arrow_up:
unittests-3.11	97.51% <100.00%> (+0.08%)	:arrow_up:
unittests-3.12	97.51% <100.00%> (+0.08%)	:arrow_up:
unittests-3.13	97.51% <100.00%> (+0.08%)	:arrow_up:
unittests-3.9	97.51% <100.00%> (+0.08%)	:arrow_up:

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