fix(timer): discard events if no eventbus causes failed delivery

[hwjiangkai]

What problem does this PR solve?

1. discard the delivery failure event when eventbus not found
2. add recover to avoid crash

Issue Number: close #191

Problem Summary

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

[codecov]

Codecov Report

Merging #239 (652ef21) into main (3f72df1) will decrease coverage by 1.16%.
The diff coverage is 96.77%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #239      +/-   ##
==========================================
- Coverage   63.50%   62.33%   -1.17%     
==========================================
  Files         118      140      +22     
  Lines       11353    12169     +816     
==========================================
+ Hits         7210     7586     +376     
- Misses       3589     4040     +451     
+ Partials      554      543      -11     

Impacted Files	Coverage Δ
internal/timer/timingwheel/timingwheel.go	78.47% <90.00%> (+0.33%)	⬆️
internal/timer/timingwheel/bucket.go	99.02% <100.00%> (+0.04%)	⬆️
internal/store/segment/server.go	13.90% <0.00%> (-27.19%)	⬇️
internal/store/block/entry.go	95.65% <0.00%> (-4.35%)	⬇️
internal/store/meta/snapshot.go	31.70% <0.00%> (ø)
internal/store/block/file/block.go
internal/store/block/file/append.go
internal/store/block/replica/replica.go
internal/store/block/file/index.go
... and 35 more

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[ifplusor]

LGTM