fix: avoid NPE when attributes are null

[ndr-brt]

What this PR changes/adds

Avoid NPEs when TP attributes are null.
The egress transformers should fail as less as possible.

Why it does that

Avoid NPE

Further notes

List other areas of code that have changed but are not necessarily linked to the main feature. This could be method
signature changes, package declarations, bugs that were encountered and were fixed inline, etc.

Linked Issue(s)

Closes #4078

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.57%. Comparing base (7f20ba5) to head (df4cabc).
Report is 192 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4079      +/-   ##
==========================================
+ Coverage   71.74%   74.57%   +2.82%     
==========================================
  Files         919      975      +56     
  Lines       18457    19967    +1510     
  Branches     1037     1120      +83     
==========================================
+ Hits        13242    14890    +1648     
+ Misses       4756     4594     -162     
- Partials      459      483      +24     

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