test: skip podcast search results without a browseId

[sigma67]

Summary

• test_many_podcasts calls yt.search("europe", filter="podcasts") and passes every result's browseId straight into get_podcast().
• Search with the podcasts filter can surface results (e.g. episodes) that don't have a browseId, since ytmusicapi/parsers/search.py:65 reads it with none_if_absent=True.
• When that happens, get_podcast(None) raises AttributeError: 'NoneType' object has no attribute 'startswith' in ytmusicapi/mixins/podcasts.py:136, failing CI (seen on PR Expose ownership for library playlists #972: https://github.com/sigma67/ytmusicapi/actions/runs/31269845020/job/93133837902).
• test_many_episodes right below already tolerates a similar case (episodes that are no longer available); this applies the same pattern here.

Test plan

• ruff check / ruff format / mypy pass via pre-commit hooks
• CI run passes (live API test, can't be run locally without credentials)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.81%. Comparing base (aa766e5) to head (91d8ef3).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #976      +/-   ##
==========================================
+ Coverage   95.77%   95.81%   +0.03%     
==========================================
  Files          47       47              
  Lines        2723     2723              
==========================================
+ Hits         2608     2609       +1     
+ Misses        115      114       -1     

Flag	Coverage Δ
unittests	95.81% <ø> (+0.03%)	⬆️

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