Prevent server crash on malformed player config entries

[marcelveldt]

What does this implement/fix?

A race between delete_player_config() and a stale player update_state() could leave a partial player config in settings.json (only default_name and values, no player_id). On the next read, get_player_configs crashed with KeyError: 'player_id', breaking the players UI until the file was manually repaired.

Changes:

• get_player_configs / get_player_config now tolerate (and auto-clean) entries missing the player_id base key, with a warning log.
• set_player_default_name and set_player_type no-op when the player config root has been deleted, so a late update_state can't resurrect a partial entry via nested set().
• remove_provider_config cleanup loop uses .get() instead of bracket access, so it survives the same kind of partial entry.

Related issue (if applicable):

• N/A

Types of changes

• Bugfix (non-breaking change which fixes an issue) — bugfix
• New feature (non-breaking change which adds functionality) — new-feature
• Enhancement to an existing feature — enhancement
• New music/player/metadata/plugin provider — new-provider
• Breaking change (fix or feature that would cause existing functionality to not work as expected) — breaking-change
• Refactor (no behaviour change) — refactor
• Documentation only — documentation
• Maintenance / chore — maintenance
• CI / workflow change — ci
• Dependencies bump — dependencies

Checklist

• The code change is tested and works locally.
• `pre-commit run --all-files` passes.
• `pytest` passes, and tests have been added/updated under `tests/` where applicable.
• For changes to shared models, the companion PR in `music-assistant/models` is linked.
• For changes affecting the UI, the companion PR in `music-assistant/frontend` is linked.
• I have read and complied with the project's AI Policy for any AI-assisted contributions.

[Copilot]

Pull request overview

This PR hardens player configuration persistence against partially-written/malformed entries in settings.json, preventing crashes in the players UI after a race between config deletion and stale player state updates.

Changes:

• Auto-detect and remove malformed player config entries missing player_id during get_player_configs, with warning logs.
• Make get_player_config more tolerant of missing player_id for unavailable players by defaulting/sanitizing fields.
• Prevent set_player_default_name and set_player_type from recreating partial config roots after deletion; make provider-config cleanup resilient to partial entries.