Reimporting of album tracks exits silently

While importing a bunch of EP's of artist "Amen Andrews", that were saved in a single folder I realise that reimporting them does not work. In this case it's got nothing to do with my previously reported "missing feature" of reimporting singleton items to regular album items (https://github.com/beetbox/beets/issues/4642), since the files are already regular album tracks.

The output below should explain what's happening but here explainend in words: When importing the first time I messed up the "CAT 138" album a little. There seem to be 2 versions of it existing on MusicBrainz. I accidently split the 2 tracks I have from this EP into each of those album versions.

I now simply want to reimport the track "Fast & Bulbous" to integrate into "CAT 138 EP", the other version of the album "CAT 138" should be deleted afterwards.

```
$ beet ls amen starbase, amen bulbous
Amen Andrews - Volume 01 - 01 - Starbase One (2003/GB) [CAT 138 EP] f:MP3-192k a:03-09/MusicBrainz |Jungle, Drum And Bass
Amen Andrews - Volume 01 - 04 - Fast & Bulbous (2003/GB) [CAT 138] f:MP3-192k a:03-09/MusicBrainz |Jungle, Techno, Drum And Bass

$ beet ls -f '$catalognum - $title, singleton:$singleton' amen starbase, amen bulbous
CAT 138 EP - Starbase One, singleton:False
CAT 138 - Fast & Bulbous, singleton:False

$ beet import -L amen bulbous
$ beet import -L -t amen bulbous
$ beet ls amen bulbous
Amen Andrews - Volume 01 - 04 - Fast & Bulbous (2003/GB) [CAT 138] f:MP3-192k a:03-09/MusicBrainz |Jungle, Techno, Drum And Bass

$ beet -vv import -L -t amen bulbous
user configuration: /home/jojo/.config/remotebeets/config.yaml
data directory: /home/jojo/.config/remotebeets
plugin paths: /home/jojo/git/whatlastgenre/plugin/beets/beetsplug
lastgenre: Loading canonicalization tree ~/git/home_config/lastgenre_conf/genres-tree.yaml
inline: adding item field disc_and_track
inline: adding item field fmt_onetrack
inline: adding item field fmt_albumtrack
inline: adding item field quality
inline: adding item field fmt_format
inline: adding item field fmt_genre
inline: adding album field incomplete
inline: adding album field is_onetrack
artresizer: method is ImageMagick
thumbnails: using ImageMagick to write metadata
thumbnails: using GIO to compute URIs
Sending event: pluginload
library database: /home/jojo/.config/remotebeets/remotebeets.db
library directory: /remote/data/music-library
Sending event: library_opened
Sending event: import_begin
beatport4: Trying beatport token loaded from file
beatport4: Beatport authorized with stored token as
Sending event: import
Sending event: cli_exit
$
```

I don't understand why the importer just silently quits instead of showing the importer prompt? Any hints what I'm missing here or is this a bug?

Start by reproducing the issue with `beet import -L -t amen bulbous` and compare the verbose output with a normal import. Trace the importer path after `import_begin` and check why it reaches `cli_exit` without showing a prompt. Done means reimporting the existing album track presents the importer prompt and applies the selected album merge.

Written by the indexing model from the issue text.