context: properly reset preBlock and preHeader

[AnnaShaleva]

I just don't believe it's possible, I was sure that I've added this resetting code. Required for https://github.com/bane-labs/go-ethereum/pull/287.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.47%. Comparing base (d01dbcb) to head (9be6f21).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #127      +/-   ##
==========================================
+ Coverage   59.42%   59.47%   +0.04%     
==========================================
  Files          32       32              
  Lines        1819     1821       +2     
==========================================
+ Hits         1081     1083       +2     
  Misses        659      659              
  Partials       79       79              

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[roman-khimov]

Huh. But consensus worked fine with blocks produced.

[AnnaShaleva]

But consensus worked fine with blocks produced.

On real network I ended up in a stale proposal starting from the second block.