fix: stream return EOF when openai return error

[liushuangls]

fix #173

[sashabaranov]

Thank you for the PR! 🔥 Looks good overall, but there are a couple of comments. Would you be able to fix those?

[codecov]

Codecov Report

Merging #184 (e82a2f5) into master (d529d13) will increase coverage by 0.47%.
The diff coverage is 93.15%.

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
+ Coverage   70.65%   71.12%   +0.47%     
==========================================
  Files          18       21       +3     
  Lines         535      568      +33     
==========================================
+ Hits          378      404      +26     
- Misses        121      125       +4     
- Partials       36       39       +3     

Impacted Files	Coverage Δ
stream_reader.go	88.88% <88.88%> (ø)
error_accumulator.go	95.23% <95.23%> (ø)
chat_stream.go	85.00% <100.00%> (+6.73%)	⬆️
stream.go	70.00% <100.00%> (-2.35%)	⬇️
unmarshaler.go	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[sashabaranov]

Wow, great work! Got a couple of comments, in any case I think we can merge now

[maplessssy]

nice. I meet the same EOF error in v1.5.2.