do not panic if the peer does not have a state in Receive

[melekes]

Peer does not have a state yet. We set it in AddPeer, but because the
peer is started before we add it to reactors, we can receive a message
before AddPeer is called.

Refs #3304

• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Updated CHANGELOG_PENDING.md

[codecov-io]

Codecov Report

Merging #3346 into develop will decrease coverage by 0.02%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           develop    #3346      +/-   ##
===========================================
- Coverage    64.03%   64.01%   -0.03%     
===========================================
  Files          215      215              
  Lines        17738    17725      -13     
===========================================
- Hits         11358    11346      -12     
+ Misses        5452     5445       -7     
- Partials       928      934       +6

Impacted Files	Coverage Δ
consensus/reactor.go	71.78% <0%> (+0.47%)	⬆️
privval/client.go	75.55% <0%> (-10%)	⬇️
libs/db/remotedb/remotedb.go	36.84% <0%> (-4.69%)	⬇️
privval/socket.go	92% <0%> (-4%)	⬇️
privval/remote_signer.go	81.51% <0%> (-1.69%)	⬇️
mempool/reactor.go	68.35% <0%> (-1.65%)	⬇️
blockchain/pool.go	78.83% <0%> (-0.69%)	⬇️
p2p/pex/pex_reactor.go	79.24% <0%> (-0.32%)	⬇️
libs/events/event_cache.go	100% <0%> (ø)	⬆️
... and 2 more

[liamsi]

Is it difficult to write a test that exposes this behaviour?

[melekes]

Yes

[unclezoro]

seems we try to fix same issue #3361

[ebuchman]

Ok let's close this for #3361 (comment) and figure out how to fix from there