fix: fix issue with runtime cancellation prior to MQTT publish

[bachya]

Describe what the PR does:

Currently, canceling the runtime before an MQTT publish occurs throws an unhandled exception.

Does this fix a specific issue?

N/A

Checklist:

• Confirm that one or more new tests are written for the new functionality.
• Run tests and ensure everything passes (with 100% test coverage).
• Update README.md with any new documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (d95a649) to head (29f7694).

Additional details and impacted files

@@            Coverage Diff            @@
##               dev      #968   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           32        32           
  Lines         1741      1744    +3     
=========================================
+ Hits          1741      1744    +3     

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