fix(api): Fix the handling of exceptions when subscribing with Kotlin Facade

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:
While testing subscription auth modes I found that exceptions during subscription would get replaced with a NPE when using the Kotlin Facade. Resolved the error so that the underlying exception gets propagated to the caller.

How did you test these changes?

• Unit test
• Verified issue could not be reproduced after change

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.01%. Comparing base (0f61cc8) to head (81f08a0).
Report is 24 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2821      +/-   ##
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+ Coverage   43.00%   44.01%   +1.00%     
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  Files         905      925      +20     
  Lines       29179    30220    +1041     
  Branches     4153     4294     +141     
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+ Hits        12549    13301     +752     
- Misses      15271    15494     +223     
- Partials     1359     1425      +66