Fix crash in task.imported_items

[JOJ0]

Description

Fixes #6291

I think it does not hurt if the imported_items() method returned an empty list instead of an throwing an exception if there is nothing in it!

To Do

• Documentation.
• Changelog.
• Tests.

[github-actions]

Thank you for the PR! The changelog has not been updated, so here is a friendly reminder to check if you need to add an entry.

[github-actions]

Thank you for the PR! The changelog has not been updated, so here is a friendly reminder to check if you need to add an entry.

[Copilot]

Pull request overview

This PR fixes a crash in the ImportTask.imported_items() method that occurred when the method was called with certain choice flags (like Action.ALBUMS, Action.TRACKS, or Action.SKIP). The issue was triggered by the importsource plugin during the import_task_choice event, which called imported_items() before items were actually imported. The fix replaces an assert False statement with a return of an empty list, which is the appropriate behavior for these edge cases.

Changes:

• Replaces assert False with return [] in the else branch of ImportTask.imported_items() method

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 68.95%. Comparing base (f9cf157) to head (d2600c3).
⚠️ Report is 2 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
beets/importer/tasks.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6326   +/-   ##
=======================================
  Coverage   68.95%   68.95%           
=======================================
  Files         140      140           
  Lines       18685    18685           
  Branches     3058     3058           
=======================================
  Hits        12885    12885           
  Misses       5153     5153           
  Partials      647      647           

Files with missing lines	Coverage Δ
beets/importer/tasks.py	90.92% <0.00%> (ø)

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