fix: remove undefined user-properties before sending Packet

[SoulKa]

Changes

• Remove undefined properties before sending packet

This fixes an error where the user sets a property to undefined which results in a TypeError (closes mqttjs/mqtt-packet#152).

[robertsLando]

@SoulKa I don't think this should be done on mqttjs side, it should be the user that ensures the properties set are not undefined

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 81.05%. Comparing base (57691cf) to head (b776a3a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lib/client.ts	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1970      +/-   ##
==========================================
- Coverage   81.15%   81.05%   -0.10%     
==========================================
  Files          24       24              
  Lines        1470     1473       +3     
  Branches      349      350       +1     
==========================================
+ Hits         1193     1194       +1     
- Misses        193      194       +1     
- Partials       84       85       +1     

Flag	Coverage Δ
unittests	81.05% <33.33%> (-0.10%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[robertsLando]

@SoulKa I have moved the issue to mqtt-packet repo. Please open a PR there