fix: fix mqtt client panic

[Yisaer]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 71.00%. Comparing base (1cc67e3) to head (46eed0d). Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3149      +/-   ##
==========================================
+ Coverage   70.97%   71.00%   +0.03%     
==========================================
  Files         398      398              
  Lines       42996    42986      -10     
==========================================
+ Hits        30513    30520       +7     
+ Misses      10088    10074      -14     
+ Partials     2395     2392       -3     

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[ngjaying]

Closes #3080