fix: dont deduplicate matches if musicbrainz ID is not set for album matches

[Neurrone]

First discussed in #4269 (reply in thread)

Description

Fixes album candidates being treated as duplicates when the album id (assumed to be musicbrainz id) is not set.

(...)

To Do

• Documentation. (If you've add a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst near the top of the document.)
• Tests. (Encouraged but not strictly required.)

[sampsyo]

Looks great to me overall! Would you mind adding a quick changelog entry, and then we can merge this?

[sampsyo]

Looks great; thanks!! Slightly tweaked the wording, but this is good to go. 🙏