fix: prevent crash during timer expiration after stream is closed

[morapet]

Reorder ticker stop and close merge to prevent send(true) happens after merge is closed, in rare situation when the timer expires exactly at the point between close(merge) and ticker.Stop()

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This is a bug
Closes #7006

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.83%. Comparing base (e67a7b6) to head (ab221c3).
Report is 25 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #19917      +/-   ##
==========================================
- Coverage   55.83%   55.83%   -0.01%     
==========================================
  Files         320      320              
  Lines       44381    44381              
==========================================
- Hits        24782    24781       -1     
- Misses      17030    17041      +11     
+ Partials     2569     2559      -10     

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[nitishfy]

Please resolve the Lint Issues for this PR by running the gofumpt command against the logs.go. Thanks!

[gdsoumya]

LGTM