Fix inserting block before base

[kamilsa]

Signed-off-by: kamilsa kamilsa16@gmail.com

Referenced issues

Related to #1218

Description of the Change

We observed that we could crash when inserting block into vote graph when it is less than base block of this graph

Benefits

Fix failure behavior

Possible Drawbacks

None

Usage Examples or Tests

Test is added

[codecov]

Codecov Report

Merging #1325 (282c593) into master (b7c0cdc) will decrease coverage by 0.02%.
The diff coverage is 42.85%.

@@            Coverage Diff             @@
##           master    #1325      +/-   ##
==========================================
- Coverage   25.73%   25.70%   -0.03%     
==========================================
  Files         594      595       +1     
  Lines       21514    21521       +7     
  Branches    11168    11169       +1     
==========================================
- Hits         5536     5532       -4     
- Misses      10861    10878      +17     
+ Partials     5117     5111       -6     

Impacted Files	Coverage Δ
.../consensus/grandpa/vote_graph/vote_graph_error.cpp	20.00% <20.00%> (ø)
...e/consensus/grandpa/vote_graph/vote_graph_impl.cpp	46.77% <100.00%> (+0.43%)	⬆️
core/metrics/impl/session_impl.cpp	37.50% <0.00%> (-8.34%)	⬇️
core/api/transport/impl/ws/ws_listener_impl.cpp	40.27% <0.00%> (-2.78%)	⬇️
core/metrics/impl/prometheus/handler_impl.cpp	26.53% <0.00%> (-2.05%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more