fix: refresh last state even no proved state

[yangby-cryptape]

Description

I didn't write unit test in #172.

p.s. 😢 Except that PR, I have written unit tests for almost all my PRs in this repo, since last year.

Sadly, It really doesn't work, just like Murphy's law said: Anything that can go wrong will go wrong.

That bugfix is incomplete.

This PR adds a unit test and fix it, again.

Commits

• test: reproduce the bug the GetLastState wasn't sent sometimes when refresh peers
• fix: refresh last state even no proved state (ref-commit: b95148c).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0a8c34a) 71.42% compared to head (030c0e4) 72.42%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #176      +/-   ##
===========================================
+ Coverage    71.42%   72.42%   +1.00%     
===========================================
  Files           25       25              
  Lines         6512     6513       +1     
===========================================
+ Hits          4651     4717      +66     
+ Misses        1861     1796      -65     

Flag	Coverage Δ
unittests	72.42% <100.00%> (+1.00%)	⬆️

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